It was on September 1, 1939 that World War II began in Europe as German troops hurtled into Poland, igniting the biggest conflagration in human history. The war, which ended in 1945, eventually involved 61 countries, claimed 50 million lives, and completely changed the geopolitical landscape. Poland, in the unenviable position of being sandwiched between Nazi Germany and the Soviet Union, disappeared from the map for the duration of the war. More than 6 million Poles died between 1939 and 1945.

1939 - 1945

World War II killed more people, destroyed more property, disrupted more lives, and probably had more far-reaching consequences than any other war in history. It brought about the downfall of Western Europe as the center of world power and led to the rise of the Soviet Union. The development of the atomic bomb during the war opened the nuclear age.

The exact number of people killed because of World War II will never be known. Military deaths probably totaled about 17 million. Civilian deaths were even greater as a result of starvation, bombing raids, massacres, epidemics, and other war-related causes. The battlegrounds spread to nearly every part of the world. Troops fought in the steaming jungles of Southeast Asia, in the deserts of northern Africa, and on islands in the Pacific Ocean. Battles were waged on frozen fields in the Soviet Union, below the surface of the Atlantic Ocean, and in the streets of many European cities.

World War II began on Sept. 1, 1939, when Germany invaded Poland. Germany's dictator, Adolf Hitler, had built Germany into a powerful war machine. That machine rapidly crushed Poland, Denmark, Luxembourg, the Netherlands, Belgium, Norway, and France. By June 1940, Great Britain stood alone against Hitler. That same month, Italy joined the war on Germany's side. The fighting soon spread to Greece and northern Africa. In June 1941, Germany invaded the Soviet Union. Japan attacked United States military bases at Pearl Harbor in Hawaii on Dec. 7, 1941, bringing the United States into the war. By mid-1942, Japanese forces had conquered much of Southeast Asia and had swept across many islands in the Pacific.

Germany, Italy, and Japan formed an alliance known as the Axis. Six other nations eventually joined the Axis. The United States, Great Britain, China, and the Soviet Union were the major powers fighting the Axis. They were called the Allies. The Allies totaled 50 nations by the end of the war.

During 1942, the Allies stopped the Axis advance in northern Africa, the Soviet Union, and the Pacific. Allied forces landed in Italy in 1943 and in France in 1944. In 1945, the Allies drove into Germany from the east and the west. A series of bloody battles in the Pacific brought the Allies to Japan's doorstep by the summer of 1945. Germany surrendered on May 7, 1945, and Japan on Sept. 2, 1945.

An uneasy peace took effect as a war-weary world began to rebuild after World War II. Much of Europe and parts of Asia lay in ruins. Millions of people were starving and homeless. Europe's leadership in world affairs had ended. The United States and the Soviet Union had become the world's most powerful nations. But their wartime alliance broke down soon after the war. New threats to peace arose as the Soviet Union sought to spread Communism in Europe and Asia.

Many historians trace the causes of World War II to problems left unsolved by World War I (1914-1918). World War I and the treaties that ended it also created new political and economic problems. Forceful leaders in several countries took advantage of those problems to seize power. The desire of dictators in Germany, Italy, and Japan to conquer additional territory brought them into conflict with democratic nations.

The Peace of Paris. After World War I ended, representatives of the victorious nations met in Paris in 1919 to draw up peace treaties for the defeated countries. The treaties, known together as the Peace of Paris, followed a long and bitter war. They were worked out in haste by countries with opposing goals and failed to satisfy even the victors. Of all the countries on the winning side, Italy and Japan left the peace conference most dissatisfied. Italy gained less territory than it felt it deserved and vowed to take action on its own. Japan gained control of German territories in the Pacific and thereby launched a program of expansion. But Japan was angered by the peacemakers' failure to endorse the principle of the equality of all races.

The countries that lost World War I -- Germany, Austria, Hungary, Bulgaria, and Turkey -- were especially dissatisfied with the Peace of Paris. They were stripped of territory and arms and were required to make reparations (payments for war damages).

The Treaty of Versailles, which was signed with Germany, punished Germany severely. The German government agreed to sign the treaty only after the victorious powers threatened to invade. Many Germans particularly resented a clause that forced Germany to accept responsibility for causing World War I.

Economic problems. World War I seriously damaged the economies of European countries. Both the winners and the losers came out of the war deeply in debt. The defeated powers had difficulty paying reparations to the victors, and the victors had difficulty repaying loans from the United States. The shift from a wartime economy to a peacetime economy caused further problems. Many soldiers could not find jobs after the war.

Italy and Japan suffered from too many people and too few resources after World War I. They eventually tried to solve their problems by territorial expansion. In Germany, runaway inflation destroyed the value of money and wiped out the savings of millions of people. In 1923, the German economy neared collapse. Loans from the United States helped Germany's government restore order. By the late 1920's, Europe appeared to be entering a period of economic stability.

A worldwide business slump known as the Great Depression began in the United States in 1929. By the early 1930's, it had halted Europe's economic recovery. The Great Depression caused mass unemployment and spread poverty and despair. It weakened democratic governments and strengthened extreme political movements that promised to end the economic problems. Two movements in particular gained strength. The forces of Communism, known as the Left, called for revolution by the workers. The forces of fascism, called the Right, favored strong national government. Throughout Europe, the forces of the Left clashed with the forces of the Right. The political extremes gained the most support in countries with the greatest economic problems and the deepest resentment of the Peace of Paris.

Nationalism was an extreme form of patriotism that swept across Europe during the 1800's. Supporters of nationalism placed loyalty to the aims of their nation above any other public loyalty. Many nationalists viewed foreigners and members of minority groups as inferior. Such beliefs helped nations justify their conquest of other lands and the poor treatment of minorities within their borders. Nationalism was a chief cause of World War I, and it grew even stronger after that war.

Nationalism went hand in hand with feelings of national discontent. The more people felt deprived of national honor, the more they wished to see their country powerful and able to insist on its rights. Many Germans felt humiliated by their country's defeat in World War I and its harsh treatment under the Treaty of Versailles. During the 1930's, they enthusiastically supported a violently nationalistic organization called the Nazi Party. The Nazi Party declared that Germany had a right to become strong again. Nationalism also gained strength in Italy and Japan.

The Peace of Paris established an international organization called the League of Nations to maintain peace. But nationalism prevented the League from working effectively. Each country backed its own interests at the expense of other countries. Only weak countries agreed to submit their disagreements to the League of Nations for settlement. Strong nations reserved the right to settle their disputes by threats or, if tough talk failed, by force.

The rise of dictatorships. The political unrest and poor economic conditions that developed after World War I enabled dictatorships to arise in several countries, especially in those countries that lacked a tradition of democratic government. During the 1920's and 1930's, dictatorships came to power in the Soviet Union, Italy, Germany, and Japan. They held total power and ruled without regard to law. The dictatorships used terror and secret police to crush opposition to their rule. People who objected risked imprisonment or execution.

In the Soviet Union, the Communists, led by V. I. Lenin, had seized power in 1917. Lenin set up a dictatorship that firmly controlled the country by the time he died in 1924. After Lenin's death, Joseph Stalin and other leading Communists struggled for power. Stalin eliminated his rivals one by one and became the Soviet dictator in 1929.

In Italy, economic distress after World War I led to strikes and riots. As a result of the violence, a strongly nationalistic group called the Fascist Party gained many supporters. Benito Mussolini, leader of the Fascists, promised to bring order and prosperity to Italy. He vowed to restore to Italy the glory it had known in the days of the ancient Roman Empire. By 1922, the Fascists had become powerful enough to force the king of Italy to appoint Mussolini premier. Mussolini, who took the title il Duce (the Leader), soon began to establish a dictatorship.

In Germany, the Nazi Party made spectacular gains as the Great Depression deepened during the early 1930's. Many Germans blamed all their country's economic woes on the hated Treaty of Versailles, which forced Germany to give up territory and resources and pay large reparations. In 1933, Adolf Hitler, the leader of the Nazis, was appointed chancellor of Germany. Hitler, who was called der Fuhrer (the Leader), soon made Germany a dictatorship. He vowed to ignore the Versailles Treaty and to avenge Germany's defeat in World War I. Hitler preached that Germans were a "superior race" and that such peoples as Jews and Slavs were inferior. He began a campaign of hatred against Jews and Communists and promised to rid the country of them. Hitler's extreme nationalism appealed to many Germans.

In Japan, military officers began to hold political office during the 1930's. By 1936, they had strong control of the government. Japan's military government glorified war and the training of warriors. In 1941, General Hideki Tojo became premier of Japan.

Aggression on the march. Japan, Italy, and Germany followed a policy of aggressive territorial expansion during the 1930's. They invaded weak lands that could be taken over easily. The dictatorships knew what they wanted, and they grabbed it. The democratic countries responded with timidity and indecision to the aggression of the dictatorships.

Japan was the first dictatorship to begin a program of conquest. In 1931, Japanese forces seized control of Manchuria, a region of China rich in natural resources. Some historians consider Japan's conquest of Manchuria as the real start of World War II. Japan made Manchuria a puppet state called Manchukuo. In 1937, Japan launched a major attack against China. It occupied most of eastern China by the end of 1938, though the two countries had not officially declared war. Japan's military leaders began to speak about bringing all of eastern Asia under Japanese control.

Italy looked to Africa to fulfill its ambitions for an empire. In 1935, Italian troops invaded Ethiopia, one of the few independent countries in Africa. The Italians used machine guns, tanks, and airplanes to overpower Ethiopia's poorly equipped army. They had conquered the country by May 1936.

Soon after Hitler took power, he began to build up Germany's armed forces in violation of the Treaty of Versailles. In 1936, Hitler sent troops into the Rhineland, a region of Germany along the banks of the Rhine River. Under the treaty, the Rhineland was to remain free of troops. In March 1938, German soldiers marched into Austria and united it with Germany. Many people in Germany and Austria welcomed that move.

The acts of aggression were easy victories for the dictatorships. The League of Nations proved incapable of stopping them. It lacked an army and the power to enforce international law. The United States had refused to join the League or become involved in European disputes. Great Britain and France were unwilling to risk another war so soon after World War I. The two powers knew they would bear the burden of any fighting.

The aggressors soon formed an alliance. In 1936, Germany and Italy agreed to support one another's foreign policy. The alliance was known as the Rome-Berlin Axis. Japan joined the alliance in 1940, and it became the Rome-Berlin-Tokyo Axis.

The Spanish Civil War. A civil war tore Spain apart from 1936 to 1939. In 1936, many of Spain's army officers revolted against the government. The army rebels chose General Francisco Franco as their leader. Franco's forces were known as Nationalists or Rebels. The forces that supported Spain's elected government were called Loyalists or Republicans. The Spanish Civil War drew worldwide attention. During the war, the dictatorships again displayed their might while the democracies remained helpless.

Hitler and Mussolini sent troops, weapons, aircraft, and advisers to aid the Nationalists. The Soviet Union was the only power to help the Loyalists. France, Britain, and the United States decided not to become involved. However, Loyalist sympathizers from many countries joined the International Brigades that the Communists formed to fight in Spain.

The last Loyalist forces surrendered on April 1, 1939, and Franco set up a dictatorship in Spain. The Spanish Civil War served as a military proving ground for World War II because Germany, Italy, and the Soviet Union used it to test weapons and tactics. The war in Spain was also a rehearsal for World War II in that it split the world into forces that either supported or opposed Nazism and Fascism.

The failure of appeasement. Hitler prepared to strike again soon after Germany absorbed Austria in March 1938. German territory then bordered Czechoslovakia on three sides. Czechoslovakia had become an independent nation after World War I. Its population consisted of many nationalities, including more than 3 million people of German descent. Hitler sought control of the Sudetenland, a region of western Czechoslovakia where most of the Germans lived. Urged on by Hitler, the Sudeten Germans began to clamor for union with Germany.

Czechoslovakia was determined to defend its territory. France and the Soviet Union had pledged their support. As tension mounted, Britain's Prime Minister Neville Chamberlain tried to restore calm. Chamberlain wished to preserve peace at all cost. He believed that war could be prevented by meeting Hitler's demands. That policy became known as appeasement.

Chamberlain had several meetings with Hitler during September 1938 as Europe teetered on the edge of war. Hitler raised his demands at each meeting. On September 29, Chamberlain and French Premier Edouard Daladier met with Hitler and Mussolini in Munich, Germany. Chamberlain and Daladier agreed to turn over the Sudetenland to Germany, and they forced Czechoslovakia to accept the agreement. Hitler promised that he had no more territorial demands.

The Munich Agreement marked the height of the policy of appeasement. Chamberlain and Daladier hoped that the agreement would satisfy Hitler and prevent war -- or that it would at least prolong the peace until Britain and France were ready for war. The two leaders were mistaken on both counts.

The failure of appeasement soon became clear. Hitler broke the Munich Agreement in March 1939 and seized the rest of Czechoslovakia. He thereby added Czechoslovakia's armed forces and industries to Germany's military might. In the months before World War II began, Germany's preparations for war moved ahead faster than did the military build-up of Britain and France.

During the first year of World War II, Germany won a series of swift victories over Poland, Denmark, Luxembourg, the Netherlands, Belgium, Norway, and France. Germany then attempted to bomb Britain into surrendering, but it failed.

The invasion of Poland. After Hitler seized Czechoslovakia, he began demanding territory from Poland. Great Britain and France pledged to help Poland if Germany attacked it. Yet the two powers could aid Poland only by invading Germany, a step that neither chose to take. Britain had only a small army. France had prepared to defend its territory, not to attack.

Great Britain and France hoped that the Soviet Union would help defend Poland. But Hitler and Stalin shocked the world by becoming allies. On Aug. 23, 1939, Germany and the Soviet Union signed a nonaggression pact -- in which they agreed not to go to war against each other. They secretly decided to divide Poland between themselves.

On Sept. 1, 1939, Germany invaded Poland and began World War II. Poland had a fairly large army but little modern equipment. The Polish army expected to fight along the country's frontiers. However, the Germans introduced a new method of warfare they called blitzkrieg (lightning war). The blitzkrieg stressed speed and surprise. Rows of tanks smashed through Poland's defenses and rolled deep into the country before the Polish army had time to react. Swarms of German dive bombers and fighter aircraft knocked out communications and pounded battle lines.

The Poles fought bravely. But Germany's blitzkrieg threw their army into confusion. On Sept. 17, 1939, Soviet forces invaded Poland from the east. By late September, the Soviet Union occupied the eastern third of Poland, and Germany had swallowed up the rest.

The Phony War. Great Britain and France declared war on Germany on Sept. 3, 1939, two days after the invasion of Poland. But the two countries stood by while Poland collapsed. France moved troops to the Maginot Line, a belt of steel and concrete fortresses it had built after World War I along its border with Germany. Britain sent a small force into northern France. Germany stationed troops on the Siegfried Line, a strip of defenses Hitler built in the 1930's opposite the Maginot Line. The two sides avoided fighting in late 1939 and early 1940. Journalists called the period the Phony War.

The conquest of Denmark and Norway. Valuable shipments of iron ore from Sweden reached Germany by way of Norway's port of Narvik. Hitler feared British plans to cut off those shipments by laying explosives in Norway's coastal waters. In April 1940, German forces invaded Norway. They conquered Denmark on the way. Britain tried to help Norway, but Germany's airpower prevented many British ships and troops from reaching the country. Norway fell to the Germans in June 1940. The conquest of Norway secured Germany's shipments of iron ore. Norway also provided bases for German submarines and aircraft.

Chamberlain, the champion of appeasement, resigned after the invasion of Norway. Winston Churchill replaced him as Britain's prime minister on May 10, 1940. Churchill told the British people he had nothing to offer them but "blood, toil, tears, and sweat."

The invasion of the Low Countries. The Low Countries -- Belgium, Luxembourg, and the Netherlands -- hoped to remain neutral after World War II began. However, Germany launched a blitzkrieg against them on May 10, 1940. The Low Countries immediately requested Allied help. But Luxembourg surrendered in one day, and the Netherlands in five days. British and French forces rushed into Belgium and fell into a German trap. As the Allied forces raced northward, the main German invasion cut behind them through the Belgian Ardennes Forest to the south. The Germans reached the English Channel on May 21. They had nearly surrounded Allied forces in Belgium.

King Leopold III of Belgium surrendered on May 28, 1940. His surrender left the Allied forces trapped in Belgium in great danger. They were retreating toward the French seaport of Dunkerque on the English Channel. Britain sent all available craft to rescue the troops. The rescue fleet included destroyers, yachts, ferries, fishing vessels, and motorboats. Under heavy bombardment, the vessels evacuated about 338,000 troops from May 26 to June 4. The evacuation of Dunkerque saved most of Britain's army. But the army left behind all its tanks and equipment. The remaining Allied troops in Dunkerque surrendered on June 4, 1940.

The fall of France. France had expected to fight along a stationary battlefront and had built the Maginot Line for its defense. But German tanks and aircraft went around the Maginot Line. The Germans passed north of the Maginot Line as they swept through Luxembourg and Belgium and into northern France in May 1940. They launched a major assault against France on June 5. The blitzkrieg sent French forces reeling backward. As France neared collapse, Italy declared war on France and Great Britain on June 10.

German troops entered Paris on June 14, 1940. The French government had already fled the capital. Paul Reynaud had become premier of France in March. Reynaud wanted to fight on. But many of his generals and cabinet officers believed that the battle for France was lost. Reynaud resigned, and a new French government agreed to an armistice (truce) on June 22.

Under the terms of the armistice, Germany occupied the northern two-thirds of France and a strip of western France along the Atlantic Ocean. Southern France remained in French control. The town of Vichy became the capital of unoccupied France. Marshal Henri Petain, a French hero of World War I, headed the Vichy government. He largely cooperated with the Germans. Then in November 1942, German troops occupied all France.

One of the French generals, Charles de Gaulle, had escaped to Britain after France fell. In radio broadcasts to France, he urged the people to carry on the fight against Germany. The troops who rallied around de Gaulle became known as the Free French forces.

The Battle of Britain. Hitler believed that Great Britain would seek peace with Germany after the fall of France. But Britain fought on alone. Hitler made preparations to cross the English Channel and invade southern England. Before the Germans could invade, however, they had to defeat Britain's Royal Air Force (RAF). The Battle of Britain, which began in July 1940, was the first battle ever fought to control the air.

In August 1940, the German air force, the Luftwaffe, began to attack RAF bases. Germany's aircraft out-numbered those of the RAF. But radar stations along England's coast provided warning of approaching German planes and helped the RAF intercept them.

Each side greatly overestimated the number of enemy planes it had shot down. By September 1940, the Luftwaffe mistakenly believed it had destroyed the RAF. The Germans then halted their strikes against RAF bases and began to bomb London and other civilian targets. They hoped to weaken civilian morale and force Britain to surrender. Air raids known as the Blitz took place nearly every night through the fall and the winter. In May 1941, Germany finally gave up its attempts to defeat Britain from the air.

Hitler's decision to end the attacks on the RAF enabled Britain to rebuild its air force. Britain's survival was immensely important later in the war because the country served as a base for the Allied liberation (freeing) of Europe from Nazi rule.

The defeats in the Balkans were serious blows to Britain. However, some historians believe that the detours into Yugoslavia and Greece were costly for Hitler because they delayed his invasion of the Soviet Union. Hitler confidently predicted victory over the Soviet Union within eight weeks, and he had failed to prepare for a winter war.

The invasion of the Soviet Union. Germany and the Soviet Union proved to be uneasy partners. Hitler viewed the Soviet Union as Germany's chief enemy. He feared Soviet ambitions to expand in eastern Europe. Hitler also wanted control of Soviet wheat fields and oil fields. His 1939 nonaggression pact with Stalin served merely to keep the Soviet Union out of the war while Germany overran western Europe.

Stalin distrusted Hitler, and he sought to obtain more naval bases and to strengthen Soviet borders. In November 1939, the Soviet Union invaded Finland. The Finns surrendered in March 1940 after a fierce fight. In the summer, the Soviet Union seized the countries of Estonia, Latvia, and Lithuania along the Baltic Sea.

Germany's invasion of the Soviet Union, which was code-named Operation Barbarossa, began on June 22, 1941. It took the Soviet Union by surprise. German tanks smashed through Soviet battle lines. During the first few weeks of the campaign, the German armies encircled and killed or captured hundreds of thousands of Soviet troops. As the Germans advanced, the Soviet people destroyed factories, dams, railroads, food supplies, and anything else that might be useful to the enemy. The Germans appeared headed for victory by late July. They then began to make mistakes.

Hitler's generals wanted to press on to Moscow. But Hitler overruled them. Instead, he reinforced the German armies heading north toward Leningrad (now St. Petersburg) and south toward the Crimean Peninsula on the Black Sea. While the Germans wasted time transferring forces, Stalin brought in fresh troops. The German advance slowed in September, though the Germans took the city of Kiev. Heavy rains fell in October, and German tanks and artillery bogged down in mud.

By November 1941, the Germans had surrounded Leningrad and had begun to encircle Moscow. They reached the suburbs of Moscow by early December. The temperature then plunged to -40 °F (-40 °C). An unusually severe Soviet winter had begun early. German troops lacked warm clothing and suffered from frostbite. Their tanks and weapons broke down in the bitter cold. Winter had saved the Soviet Union.

The Battle of the Atlantic. Britain's survival in World War II depended on shipments of food, war materials, and other supplies across the Atlantic Ocean from North America. Throughout the war, Germany tried to destroy such shipments, while Britain struggled to keep its Atlantic shipping lanes open.

Germany's surface fleet was far too weak to challenge Britain's Royal Navy in battle during World War II. But individual German battleships attacked British cargo vessels. The Royal Navy hunted down and sank such raiders one by one. The biggest operation was against the powerful German battleship Bismarck. In May 1941, a fleet of British warships chased, trapped, and finally sank the Bismarck about 600 miles off the coast of France. Afterward, Germany rarely allowed its large warships to leave harbor.

The greatest threat to British shipping came from German submarines, called Unterseeboote or U-boats. The U-boats prowled the Atlantic, torpedoing any Allied cargo ships they spotted. The conquest of Norway and of France gave Germany excellent bases for its U-boats. To combat the U-boats, Britain began to use a convoy system. Under that system, cargo ships sailed in large groups escorted by surface warships. But Britain had few such ships available for escort duty.

From 1940 to 1942, Germany appeared to be winning the Battle of the Atlantic. Each month, U-boats sank thousands of tons of Allied shipping. But the Allies gradually overcame the U-boat danger. They used radar and an underwater detection device called sonar to locate German submarines. Long-range aircraft bombed U-boats as they surfaced. Shipyards in North America stepped up their production of warships to accompany convoys. By mid-1943, the Allies were sinking U-boats faster than Germany could replace them. The crisis in the Atlantic had passed.

After World War II began in Europe in 1939, President Franklin D. Roosevelt announced the neutrality of the United States. Canada declared war on Germany almost at once. As part of the British Commonwealth of Nations, it entered the war on Sept. 10, 1939, one week after Great Britain did.

The majority of people in the United States thought that their country should stay out of World War II. Yet most Americans hoped for an Allied victory. Roosevelt and other interventionists urged all aid "short of war" to nations fighting the Axis. They argued that an Axis victory would endanger democracies everywhere. Isolationists, on the other hand, opposed U.S. aid to warring nations. They accused Roosevelt of steering the nation into a war it was not prepared to fight.

All the countries in North and South America eventually declared war on the Axis. But only Brazil, Canada, Mexico, and the United States sent troops. The United States played a key role in the final Allied victory.

The arsenal of democracy. Roosevelt hoped to defeat the Axis powers by equipping the nations fighting them with ships, tanks, aircraft, and other war materials. Roosevelt appealed to the United States to become what he called "the arsenal of democracy."

At the start of World War II, U.S. neutrality laws forbade the sale of arms to warring nations. Congress soon changed the laws to help Britain and France. A new law permitted warring nations to buy arms for cash. But by late 1940, Britain had nearly run out of funds for arms. Roosevelt then proposed the Lend-Lease Act, which would permit him to lend or lease raw materials, equipment, and weapons to any nation fighting the Axis. Congress approved the act in March 1941. In all, 38 nations received a total of about $50 billion in aid under Lend-Lease. More than half the aid went to the British Empire and about a fourth to the Soviet Union.

Japan attacks. Japan, not Germany, finally plunged the United States into World War II. By 1940, Japanese forces were bogged down in China. The Chinese government, led by Chiang Kai-shek, had fled to central China. But China refused to give up. To force China to surrender, Japan decided to cut off supplies reaching China from Southeast Asia. Japan also wanted the rich resources of Southeast Asia for itself. Japan's military leaders spoke of building an empire, which they called the Greater East Asia Co-Prosperity Sphere.

The United States opposed Japan's expansion in Southeast Asia. In 1940, Japanese troops occupied northern Indochina (today part of Laos and Vietnam). In response, the United States cut off important exports to Japan. Japanese industries relied heavily on petroleum, scrap metal, and other raw materials from the United States. Tension rose after Japan seized the rest of Indochina in 1941. Roosevelt then barred the withdrawal of Japanese funds from American banks.

General Hideki Tojo became premier of Japan in October 1941. Tojo and Japan's other military leaders realized that only the United States Navy had the power to block Japan's expansion in Asia. They decided to cripple the U.S. Pacific Fleet with one forceful blow.

On Dec. 7, 1941, Japanese aircraft attacked without warning the U.S. Pacific Fleet at anchor in Pearl Harbor in Hawaii. The bombing of Pearl Harbor was a great success for Japan at first. It disabled much of the Pacific Fleet and destroyed many aircraft. But in the long run, the attack on Pearl Harbor proved disastrous for Japan. It propelled enraged Americans to arms.

The United States, Canada, and Great Britain declared war on Japan on Dec. 8, 1941. The next day, China declared war on the Axis. Germany and Italy declared war on the United States on December 11. World War II had become a global conflict.

Allied defeats in Europe ended late in 1941. Soviet forces held off the German advance in eastern Europe in 1942 and won a major victory at Stalingrad in 1943. The Allies invaded northern Africa in 1942 and forced Italy to surrender in 1943. Allied troops swarmed ashore in 1944 in northern France in the largest seaborne invasion in history. Allied attacks from the east and the west forced Germany to surrender in 1945.

The strategy. Churchill, Roosevelt, and Stalin -- the leaders of the three major Allied powers -- were known during World War II as the Big Three. The Big Three and their military advisers planned the strategy that defeated the Axis. Churchill and Roosevelt conferred frequently on overall strategy. Stalin directed the Soviet war effort but rarely consulted his allies.

Roosevelt relied heavily on his military advisers, the Joint Chiefs of Staff. They consisted of General of the Army Henry H. Arnold, commanding general of the Army Air Forces; General of the Army George C. Marshall, chief of staff of the Army; Fleet Admiral Ernest J. King, chief of naval operations; and Fleet Admiral William D. Leahy, Roosevelt's chief of staff. Churchill had a similar advisory body.

The main wartime disagreement among the Big Three concerned an Allied invasion of western Europe. Stalin constantly urged Roosevelt and Churchill to open a second fighting front in western Europe and thus draw German troops from the Soviet front. Both Roosevelt and Churchill supported the idea but disagreed on where and when to invade. The Americans wanted to land in northern France as soon as possible. The British argued that an invasion of France before the Allies were fully prepared would be disastrous. Instead, Churchill favored invading Italy first. His view won out.

Roosevelt and Churchill first met in August 1941 aboard ship off the coast of Newfoundland. They issued the Atlantic Charter, a statement of the postwar aims of the United States and Great Britain. After the Japanese attacked Pearl Harbor, Roosevelt and Churchill conferred in Washington, D.C. The two leaders felt that Germany was a nearer and a more dangerous enemy than Japan. They decided to concentrate on defeating Germany first.

In January 1943, Roosevelt and Churchill met in Casablanca, Morocco. They agreed to invade the Mediterranean island of Sicily after driving the Germans and Italians from northern Africa. At the conference, Roosevelt announced that the Allies would accept only unconditional (complete) surrender from the Axis powers. Churchill supported him.

Roosevelt and Churchill first met with Stalin in November 1943 in Teheran, Iran. The Big Three discussed plans for a joint British and American invasion of France in the spring of 1944. They did not meet again until Germany neared collapse. In February 1945, Roosevelt, Churchill, and Stalin gathered at Yalta, a Soviet city on the Crimean Peninsula. They agreed that their countries would each occupy a zone of Germany after the war. France was to occupy a fourth zone. At the Yalta Conference, Stalin pledged to permit free elections in Poland and other countries in eastern Europe after the war. He later broke that pledge. Roosevelt died in April 1945, two months after the Yalta Conference.

On the Soviet front. Soviet forces struck back at the Germans outside Moscow in December 1941. The Soviet troops pushed the invaders back about 100 miles from Moscow during the winter. The Germans never again came so close to Moscow as they had been in December 1941. However, the Soviet recovery was short lived.

In the spring of 1942, the Germans again attacked. They overran the Crimean Peninsula and headed eastward toward Soviet oil fields in the Caucasus region. Hitler ordered General Friedrich von Paulus to press on and to take the city of Stalingrad (now Volgograd). A savage five-month battle for Stalingrad began in late August. By September, German and Soviet soldiers were fighting hand to hand in the heart of the city.

With winter approaching, Paulus asked permission to pull back from Stalingrad. Hitler ordered him to hold on and fight. Soviet troops counterattacked in mid-November. Within a week, they had trapped Paulus' army. The Luftwaffe promised to supply the army by air. But few supplies landed. Each day, thousands of German soldiers froze or starved to death. On Feb. 2, 1943, the last German troops in Stalingrad surrendered.

The Battle of Stalingrad marked a turning point in World War II. It halted Germany's eastward advance. About 300,000 German troops were killed or captured. An enormous number of Soviet soldiers also died.

In northern Africa. The Germans took a beating in northern Africa about the same time as their defeat at Stalingrad. In the summer of 1942, German and Italian forces led by Rommel faced the British at El Alamein, Egypt. General Harold Alexander and Lieutenant General Bernard L. Montgomery commanded the British forces in northern Africa.

Rommel attacked in late August 1942 at Alam el Halfa, south of El Alamein. The British halted the attack, partly because they had secretly learned of Rommel's battle plan. Churchill called for an immediate counterattack. But Montgomery refused to rush into battle before he was fully prepared. On October 23, Montgomery struck at El Alamein. He had broken through the enemy lines by early November. The Axis forces retreated toward Tunisia with the British in hot pursuit. The Battle of El Alamein, like the Battle of Stalingrad, marked a turning point in the war. In both battles, the Allies ended Hitler's string of victories.

Soon after the Battle of El Alamein, the Allies invaded French colonies in northern Africa. Allied troops commanded by Lieutenant General Dwight D. Eisenhower of the United States landed in Algeria and Morocco on Nov. 8, 1942. Vichy French forces in northern Africa fought back for a few days. They then joined the Allied side.

The Allies hoped to advance rapidly into Tunisia and thereby cut off the Axis forces from their home bases in Italy and Sicily. But Axis troops moved faster and seized Tunisia first. There, Rommel prepared for battle. American troops first engaged in combat with the Germans in February 1943 near Kasserine Pass in northern Tunisia. Rommel defeated the inexperienced Americans in hard fighting. But thereafter, the Allies steadily closed in. The last Axis forces in northern Africa surrendered in May. Rommel had already returned to Germany. By clearing the Axis forces from northern Africa, the Allies obtained bases from which to invade southern Europe.

The air war. Before World War II began, some aviation experts claimed that the long-range bomber was the most advanced weapon in the world. They believed that bombers could wipe out cities and industries and so destroy an enemy's desire and ability to go on fighting. Their theory was tested during World War II.

The first great air battle in history opened in 1940 between Germany's Luftwaffe and Britain's Royal Air Force. During the Battle of Britain, Marshal Hermann Goering, commander of the Luftwaffe, failed to defeat Britain from the air. RAF fighter planes, including Spitfires and Hurricanes, helped win the Battle of Britain by shooting down German bombers. By May 1941, the bombing of Britain had largely stopped. But RAF bombers pounded Germany until the end of the war.

At first, Britain's bombing campaign was costly and ineffective. The RAF relied on area bombing in the hope of hitting a target by plastering the area with bombs. It favored nighttime raids, which were safer than daytime raids. But pilots often missed their targets in the dark. In 1942, Britain turned to saturation bombing of German cities. About 900 bombers battered Cologne on May 30, 1942, in the first such massive raid.

The United States joined the air war against Germany in 1942. The American B-17 bomber carried a better bombsight than British planes. B-17's were known as Flying Fortresses because of their heavy armor and many guns, and they could take much punishment. For those reasons, the Americans favored pinpoint bombing of specific targets during daytime rather than area bombing at night. From 1943 until the end of the war, bombs rained down on Germany around the clock.

In spite of the massive bombardment, German industries continued to increase production, and German morale failed to crack. The air war achieved its goals only during the last 10 months of World War II. In that time, nearly three times as many bombs fell on Germany as in all the rest of the war. By the end of the war, Germany's cities lay in ruins. Its factories, refineries, railroads, and canals had nearly ceased to operate. Hundreds of thousands of German civilians had been killed. Millions more were homeless. The bomber had finally become the weapon its supporters had foreseen.

Germany's air defenses rapidly improved during World War II. The Germans used radar to spot incoming bombers, and they used fighter aircraft to shoot them down. In 1944, Germany introduced the first jet fighter, the Messerschmitt Me-262. The fast plane could easily overtake the propeller-driven fighters of the Allies. But Hitler failed to use jet fighters effectively, which kept Germany from gaining an advantage in the air war.

In 1944, Germany used the first guided missiles against Britain. The V-1 and V-2 missiles caused great damage and took many lives. But the Germans introduced the weapons too late to affect the war's outcome.

The invasion of Italy. The Allies planned to invade Sicily after driving the Axis forces out of northern Africa. Axis planes bombed Allied ships in the Mediterranean Sea from bases in Sicily. The Allies wanted to make the Mediterranean safe for their ships. They also hoped that an invasion of Sicily might knock a war-weary Italy out of the war.

Allied forces under Eisenhower landed along Sicily's south coast on July 10, 1943. For 39 days, they engaged in bitter fighting with German troops over rugged terrain. The last Germans left Sicily on August 17.

Mussolini fell from power on July 25, 1943, after the invasion of Sicily. The Italian government imprisoned Mussolini, but German paratroopers later rescued him. Italy's new premier, Field Marshal Pietro Badoglio, began secret peace talks with the Allies. Badoglio hoped to prevent Italy from becoming a battleground. Italy surrendered on September 3. However, Field Marshal Albert Kesselring, Germany's commander in the Mediterranean region, was determined to fight the Allies for control of Italy.

Allied forces led by Lieutenant General Mark W. Clark of the United States landed at Salerno, Italy, on Sept. 9, 1943. They fought hard just to stay ashore. Another Allied force had already landed farther south. The Allies slowly struggled up the Italian Peninsula in a series of head-on assaults against well-defended German positions. By early November, the Allies had nearly reached Cassino, about 75 miles south of Rome. But they failed to pierce German defenses there. Some of the most brutal fighting of World War II occurred near Cassino.

In January 1944, the Allies landed troops at Anzio, west of Cassino, in an effort to attack the Germans from behind. However, German forces kept the Allies pinned down on the beaches at Anzio for four months. Thousands of Allied soldiers died there.

The Allies finally broke through German defenses in Italy in May 1944. Rome fell on June 4. The Germans held their positions in northern Italy through the fall and winter. But in the spring, the Allies swept toward the Alps. German forces in Italy surrendered on May 2, 1945. Mussolini had been captured and shot by Italian resistance fighters on April 28.

D-Day. Soon after the evacuation of Dunkerque in 1940, Great Britain started to plan a return to France. In 1942, the United States and Britain began to discuss a large-scale invasion across the English Channel. That summer, the Allies raided the French port of Dieppe on the channel. The raiders met strong German defenses and suffered heavy losses. The Dieppe raid convinced the Allies that landing on open beaches had a better chance of success than landing in a port.

Throughout 1943, preparations moved ahead for an invasion of northern France the following year. The invasion plan received the code name Operation Overlord. The Allies assembled huge amounts of equipment and great numbers of troops for Overlord in southern England. General Dwight D. Eisenhower was selected to command the invasion.

The Germans expected an Allied invasion along the north coast of France in 1944. But they were unsure where. A chain of fortifications, which the Germans called the Atlantic Wall, ran along the coast. Hitler placed Rommel in charge of strengthening German defenses along the English Channel. Rommel brought in artillery, mined the water and the beaches, and strung up barbed wire. The Germans concentrated their troops near Calais, at the narrowest part of the English Channel. But the Allies planned to land farther west, in a region of northern France called Normandy.

Eisenhower chose Monday, June 5, 1944, as D-Day -- the date of the Normandy invasion. Rough seas forced him to postpone D-Day until June 6. During the night, about 2,700 ships carrying landing craft and 176,000 soldiers crossed the channel. Minesweepers had gone ahead to clear the water. Paratroopers dropped behind German lines to capture bridges and railroad tracks. At dawn, battleships opened fire on the beaches. At 6:30 A.M., troops from the United States, Britain, Canada, and France stormed ashore on a 60-mile front in the largest seaborne invasion in history.

D-Day took the Germans by surprise. But they fought back fiercely. At one landing site, code-named Omaha Beach, U.S. troops came under heavy fire and barely managed to stay ashore. Nevertheless, all five Allied landing beaches were secure by the end of D-Day. The Allies soon had an artificial harbor in place for unloading more troops and supplies. A pipeline carried fuel across the channel. By the end of June 1944, about a million Allied troops had reached France.

The Allied forces advanced slowly at first. The Americans struggled westward to capture the badly needed port of Cherbourg. British and Canadian soldiers fought their way to Caen. The battle for Cherbourg ended on June 27. Caen, which the British hoped to capture on D-Day, fell on July 18. Near the end of July, the Allies finally broke through German lines into open country.

The drive to the Rhine. On July 25, 1944, Allied bombers blasted a gap in the German front near St.-Lo, about 50 miles southeast of Cherbourg. The U.S. Third Army under Lieutenant General George S. Patton plowed through the hole. The battlefield had opened up. During August, the Allies cleared the Germans out of most of northwestern France. Allied bombers hounded the retreating Germans.

Patton's army rolled eastward toward Paris. On Aug. 19, 1944, Parisians rose up against the occupying German forces. Hitler ordered the city destroyed. But his generals delayed carrying out the order. American and Free French forces liberated Paris on August 25.

In mid-August 1944, Allied forces landed in southern France. They moved rapidly up the Rhone River Valley. Meanwhile, Patton raced eastward toward the German border and the Rhine River. In late August, his tanks ran out of fuel. To the north, British forces led by Field Marshal Bernard L. Montgomery swept into Belgium and captured Antwerp on September 4. The Allies planned a daring airborne operation to carry them across the Rhine. On September 17, about 20,000 paratroopers dropped behind German lines to seize bridges in the Netherlands. But bad weather and other problems hampered the operation. It became clear that victory over Germany would have to wait until 1945.

Germany's generals knew they were beaten. But Hitler pulled his failing resources together for another assault. On Dec. 16, 1944, German troops surprised and overwhelmed the Americans in the Ardennes Forest in Belgium and Luxembourg. However, the Germans lacked the troops and fuel to turn their thrust into a breakthrough. Within two weeks, the Americans stopped the German advance near the Meuse River in Belgium. The Ardennes offensive is also known as the Battle of the Bulge because of the bulging shape of the battleground on a map.

The Soviet advance. The Soviet victory in the Battle of Stalingrad ended Germany's progress in eastern Europe. After January 1943, Soviet soldiers slowly pushed the Germans back. Soviet forces had improved by 1943, and they greatly outnumbered the opposing German armies. Supplies poured into the Soviet Union from Britain and the United States, and Soviet factories had geared up for wartime production.

Nevertheless, the Germans returned to the offensive in July 1943 near the Soviet city of Kursk. They massed about 3,000 tanks for the assault. Soviet forces lay waiting for them. In one of the greatest tank battles in history, Soviet mines, tanks, antitank guns, and aircraft blew apart many German tanks. Hitler finally called off the attack to save his remaining tanks.

Soviet troops moved slowly forward during the summer and fall of 1943. In January 1944, a Soviet offensive ended the siege of Leningrad, which had begun in September 1941. About a million Leningraders died during the siege, mostly from lack of food and heat. But the city never surrendered.

In June 1944, soon after the Normandy invasion, Stalin's armies attacked along a 450-mile front. By late July, Soviet troops had reached the outskirts of Warsaw. Poland's Home Army rose up against German forces in Warsaw on August 1. But Soviet troops refused to come to Poland's aid. Stalin permitted the Germans to destroy the Home Army, which might have resisted his plans to set up a Communist government in Poland after the war. The Home Army surrendered after two months. More than 200,000 Poles died during the Warsaw uprising. Soviet forces entered Warsaw in January 1945.

Meanwhile, Soviet troops drove into Romania and Bulgaria. The Germans pulled out of Greece and Yugoslavia in the fall of 1944 but held out in Budapest, the capital of Hungary, until February 1945. Vienna, Austria's capital, fell to Soviet soldiers in April. By then, Soviet troops occupied nearly all of eastern Europe.

Victory in Europe. The Allies began their final assault on Germany in early 1945. Soviet soldiers reached the Oder River, about 40 miles east of Berlin, in January. Allied forces in the west occupied positions along the Rhine by early March.

British and Canadian forces cleared the Germans out of the Netherlands and swept into northern Germany. American and French forces raced toward the Elbe River in central Germany. Hitler ordered his soldiers to fight to the death. But large numbers of German soldiers surrendered each day.

As they advanced, the Allies discovered horrifying evidence of Nazi brutality. Hitler had ordered the imprisonment and murder of millions of Jews and members of other minority groups in concentration camps. The starving survivors of the death camps gave proof of the terrible suffering of those who had already died.

The capture of Berlin, then Germany's capital, was left to Soviet forces. By April 25, 1945, Soviet troops had surrounded the city. From a bunker (shelter) deep underground, Hitler ordered German soldiers to fight on. On April 30, however, Hitler committed suicide. He remained convinced that his cause had been right but that the German people had proven unworthy of his rule.

Grand Admiral Karl Doenitz briefly succeeded Hitler as the leader of Germany. Doenitz arranged for Germany's surrender. On May 7, 1945, Colonel General Alfred Jodl, chief of staff of the German armed forces, signed a statement of unconditional surrender at Eisenhower's headquarters in Reims, France. World War II had ended in Europe. The Allies declared May 8 as V-E Day, or Victory in Europe Day.

Meanwhile, Japanese forces had advanced into southern Burma. China sent troops into Burma to help Britain hold onto the Burma Road. Weapons, food, and other goods traveled over that supply route from India to China. In April 1942, Japan seized and shut down the Burma Road. The Japanese had driven Allied forces from most of Burma by mid-May.

Only the conquest of the Philippines took longer than Japan expected. Japan had begun landing troops in the Philippines on Dec. 10, 1941. American and Philippine forces commanded by U.S. General Douglas MacArthur defended the islands. In late December, MacArthur's forces abandoned Manila, the capital of the Philippines, and withdrew to nearby Bataan Peninsula. Although suffering from malnutrition and disease, they beat back Japanese attacks for just over three months.

President Roosevelt ordered MacArthur to Australia, and he left the Philippines in March 1942. He promised the Filipinos, "I shall return." On April 9, about 75,000 exhausted troops on Bataan surrendered to the Japanese. Most of them were forced to march about 65 miles to prison camps. Many prisoners died of disease and mistreatment during what became known as the Bataan Death March. Some soldiers held out on Corregidor Island, near Bataan, until May 6. By then, the Japanese were victorious everywhere.

Japan's string of quick victories astonished even the Japanese. It terrified the Allies. The fall of the Netherlands Indies left Australia unprotected. The capture of Burma brought the Japanese to India's border. Australia and India feared invasion. Japanese planes bombed Darwin on Australia's north coast in February 1942.

The tide turns. Three events in 1942 helped turn the tide against Japan. They were (1) the Doolittle raid, (2) the Battle of the Coral Sea, and (3) the Battle of Midway.

The Doolittle raid. To show that Japan could be beaten, the United States staged a daring bombing raid on the Japanese homeland. On April 18, 1942, Lieutenant Colonel James H. Doolittle led 16 B-25 bombers in a surprise attack on Tokyo and other Japanese cities. The bombers took off from the deck of the Hornet, an aircraft carrier more than 600 miles east of Japan. The raid did very little damage. But it alarmed Japan's leaders, who had believed that their homeland was safe from Allied bombs. To prevent future raids, the Japanese determined to capture more islands to the south and the east and so extend the country's defenses. They soon found themselves in trouble.

The Battle of the Coral Sea. In May 1942, a Japanese invasion force sailed toward Australia's base at Port Moresby on the south coast of the island of New Guinea. Port Moresby lay at Australia's doorstep. American warships met the Japanese force in the Coral Sea, northeast of Australia. The Battle of the Coral Sea, fought from May 4 to 8, was unlike all earlier naval battles. It was the first naval battle in which opposing ships never sighted one another. Planes based on aircraft carriers did all the fighting. Neither side won a clear victory. But the battle halted the assault on Port Moresby and temporarily checked the threat to Australia.

The Battle of Midway. Japan next sent a large fleet to capture Midway Island at the westernmost tip of the Hawaiian chain. The United States had cracked Japan's naval code and thus learned about the coming invasion. Admiral Chester W. Nimitz, commander of the U.S. Pacific Fleet, gathered the ships that had survived the raid on Pearl Harbor and the Battle of the Coral Sea. He prepared to ambush the Japanese.

The Battle of Midway opened on June 4, 1942, with a Japanese bombing raid on Midway. Outdated U.S. bombers flew in low and launched torpedoes against Japanese warships. But Japanese guns downed most of the slow-moving planes. American dive bombers swooped in next. They pounded enemy aircraft carriers while their planes refueled on deck. During the three-day battle, the Japanese lost 4 aircraft carriers and more than 200 planes and skilled pilots. Japan sank 1 U.S. aircraft carrier and shot down about 150 U.S. planes.

The Battle of Midway was the first clear Allied victory over Japan in World War II. Aircraft carriers had become the most important weapon in the war in the Pacific. Japan's naval power was crippled by the loss of 4 of its 9 aircraft carriers.

Although Japan failed to capture Midway, it seized two islands at the tip of Alaska's Aleutian chain on June 7, 1942. The Americans drove the Japanese out of the Aleutians in the spring and summer of 1943.

The South Pacific. After the Battle of Midway, the Allies were determined to stop Japanese expansion in the South Pacific. In the battles that followed, American soldiers and marines fought many jungle campaigns on Pacific islands. The jungle itself was a terrifying enemy. Heavy rains drenched the troops and turned the jungle into a foul-smelling swamp. The men had to hack their way through tangled, slimy vegetation and wade through knee-deep mud. The Japanese hid everywhere, waiting to shoot unsuspecting servicemen. Scorpions and snakes were a constant menace. Malaria and other tropical diseases took a heavy toll.

The Americans also encountered Japan's strict military code in the South Pacific. The code required Japanese soldiers to fight to the death. Japanese soldiers believed that surrender meant disgrace, and the Allies rarely captured them alive. When cornered, the Japanese sometimes charged at Allied troops in nighttime suicide attacks. Rather than admit defeat, Japan's military leaders took their lives by stabbing themselves in the abdomen according to the tradition of hara-kiri.

The Allies developed two major campaigns against Japan in the South Pacific. One force under MacArthur checked the Japanese on New Guinea. Another force under Nimitz battled the Japanese in the Solomon Islands northeast of Australia. MacArthur and Nimitz aimed at taking the port of Rabaul on New Britain. Rabaul was Japan's chief base in the South Pacific. Japanese aircraft and warships attacked Allied ships from Rabaul, and Japan supplied other islands in the South Pacific from that base.

New Guinea. In the summer of 1942, Japanese troops began an overland drive across New Guinea's rugged, jungle-covered mountains to the Australian base of Port Moresby on the south coast. An Allied force made up chiefly of Australians quickly counterattacked. By November, the Japanese had been pushed back across the mountains. MacArthur then attacked Japanese positions along the north coast in a series of brilliant operations that combined air, sea, and land forces. Brutal fighting continued on New Guinea until mid-1944.

Guadalcanal. On Aug. 7, 1942, U.S. marines invaded the island of Guadalcanal in the first stage of a campaign in the Solomon Islands. The Japanese were building an air base on Guadalcanal from which to attack Allied ships. The invasion took the Japanese by surprise. But they fought back, and a fierce battle developed.

The six-month battle for Guadalcanal was one of the most vicious campaigns of World War II. Each side depended on its navy to land supplies and troop reinforcements. In a series of naval battles, the Allies gained control of the waters surrounding Guadalcanal. They then cut off Japanese shipments. Until that time, Allied supplies had been short, and the marines had depended on rice captured from the enemy. By February 1943, the starving Japanese had evacuated Guadalcanal.

After taking Guadalcanal, American forces led by Admiral William F. Halsey worked their way up the Solomon Islands. In November 1943, the Americans reached Bougainville at the top of the island chain. They defeated the Japanese there in March 1944.

Rabaul. In the summer of 1943, Allied military leaders canceled the invasion of Rabaul. Instead, American bombers pounded the Japanese base, and aircraft and submarines sank shipments headed for Rabaul. About 100,000 Japanese defenders waited there for an attack that never came. The Allies spared many lives by isolating Rabaul rather than capturing it.

Island hopping in the Central Pacific. From late 1943 until the fall of 1944, the Allies hopped from island to island across the Central Pacific toward the Philippines. During the island-hopping campaign, the Allies became expert at amphibious (seaborne) invasions Each island they captured provided a base from which to strike the next target. But rather than capture every island, the Allies by-passed Japanese strongholds and invaded islands that were weakly held. That strategy, known as leapfrogging, saved time and lives. Leapfrogging carried the Allies across the Gilbert, Marshall, Caroline, and Mariana islands in the Central Pacific.

Admiral Nimitz selected the Gilbert Islands as the first major objective in the island-hopping campaign. American marines invaded Tarawa in the Gilberts in November 1943. The attackers met heavy fire from Japanese troops in concrete bunkers. But they inched forward and captured the tiny island after four days of savage fighting. About 4,500 Japanese soldiers died defending the island. Only 17 remained alive. More than 3,000 marines were killed or wounded in the assault. The Allies improved their amphibious operations because of lessons they had learned at Tarawa. As a result, fewer men died in later landings.

In February 1944, U.S. marines and infantrymen leaped north to the Marshall Islands. They captured Kwajalein and Enewetak in relatively smooth operations. Allied military leaders meanwhile had decided to by-pass Truk, a key Japanese naval base in the Caroline Islands west of the Marshalls. They bombed Truk instead and made it unusable as a base.

The Americans made their next jump to the Mariana Islands, about 1,000 miles northwest of Enewetak. Bitter fighting for the Marianas began in June 1944. In the Battle of the Philippine Sea on June 19 and 20, Japan's navy once again attempted to destroy the U.S. Pacific Fleet. During the battle, which was fought near the island of Guam, the Allies massacred Japan's navy and destroyed its airpower. Japan lost 3 aircraft carriers and about 480 airplanes, or more than three-fourths of the planes it sent into battle. The loss of so many trained pilots was also a serious blow to Japan.

By August 1944, American forces occupied Guam, Saipan, and Tinian -- the three largest islands in the Marianas. The occupation of the Marianas brought Nimitz' forces within bombing distance of Japan. Tojo resigned as Japan's prime minister in July 1944 after the loss of Saipan. In November, American B-29 bombers began using bases in the Marianas to raid Japan.

A final hop before the invasion of the Philippines took U.S. forces to the Palau Islands in September 1944. The islands lie between the Marianas and the Philippines. The attackers met stiff resistance on Peleliu, the chief Japanese base in the Palaus. About 25 per cent of the Americans were killed or injured in a month-long fight.

The Liberation of the Philippines. The campaigns in New Guinea and the Central Pacific brought the Allies within striking distance of the Philippine Islands. MacArthur and Nimitz combined their forces to liberate the Philippines. Allied leaders decided to invade the island of Leyte in the central Philippines in the fall of 1944.

The Allies expected the Japanese to fight hard to hold the Philippines. They therefore assembled the largest landing force ever used in the Pacific campaigns. About 750 ships participated in the invasion of Leyte, which began on Oct. 20, 1944. It had taken MacArthur more than 21/2 years and many brutal battles to keep his pledge to return to the Philippines.

While Allied troops poured ashore on Leyte, Japan's navy tried yet again to crush the Pacific Fleet. The Battle for Leyte Gulf, which was fought from Oct. 23 through 26, 1944, was the the greatest naval battle in history in total tonnage. In all, 282 ships took part. The battle ended in a major victory for the United States. Japan's navy was so badly damaged that it was no longer a serious threat for the rest of the war.

During the Battle for Leyte Gulf, the Japanese unleashed a terrifying new weapon -- the kamikaze (suicide pilot). Kamikazes crashed planes filled with explosives onto Allied warships and died as a result. Many kamikazes were shot down before they crashed. But others caused great damage. The kamikaze became one of Japan's major weapons during the rest of the war.

The fight for Leyte continued until the end of 1944. On Jan. 9, 1945, the Allies landed on the island of Luzon and began to work their way toward Manila. The city fell in early March. The remaining Japanese troops on Luzon pulled back to the mountains and went on fighting until the war ended.

About 350,000 Japanese soldiers died during the campaign in the Philippines. American casualties numbered nearly 14,000 dead and about 48,000 wounded or missing. Japan was clearly doomed to defeat after losing the Philippines. But it did not intend to surrender.

The China-Burma-India theater. While fighting raged in the Pacific, the Allies also battled the Japanese on the Asian mainland. The chief theater of operations (area of military activity) involved China, Burma, and India. By mid-1942, Japan held much of eastern and southern China and had conquered nearly all Burma. The Japanese had closed the Burma Road, the overland supply route from India to China. China lacked equipment and trained troops and barely managed to go on fighting. But the Western Allies wanted to keep China in the war because the Chinese tied down hundreds of thousands of Japanese troops. For three years, the Allies flew war supplies over the world's tallest mountain system, the Himalaya, from India to China. The route was known as "the Hump."

China. By 1942, five years after Japan had invaded China, the opposing armies were near exhaustion. Japanese troops staged attacks especially to capture China's food supplies for themselves and to starve the country into surrender. As a result, millions of Chinese people died from lack of food during the war.

A struggle between China's Nationalist government, headed by Chiang Kai-shek, and Chinese Communists further weakened the country's war effort. At first, the Nationalist forces and the Communists had joined in fighting the Japanese invaders. But their cooperation gradually broke down as they prepared to fight each other after the war.

The United States sent military advisers as well as equipment to China. Colonel Claire L. Chennault, for example, trained pilots and established an air force in China. By the end of 1943, his pilots controlled the skies over China. But they could not help exhausted Chinese troops on the ground. Major General Joseph W. Stilwell served as Chiang's chief of staff and trained the Chinese army. Stilwell also commanded the U.S. forces in China and Burma.

Burma. The Allied campaign in Burma was closely linked to the fighting in China. From 1943 until early 1945, the Allies fought to recapture Burma from the Japanese and reopen a land route to China. But rugged jungle, heavy rains, and a shortage of troops and supplies hampered the Allies in Burma.

Admiral Louis Mountbatten of Great Britain became supreme Allied commander in Southeast Asia in August 1943. He directed several successful offensives in Burma in late 1943 and in 1944. By the end of 1944, Allied forces had battled their way through the jungles of northern Burma. They opened a supply route across northern Burma to China in January 1945. Rangoon, Burma's capital, fell to the Allies in May. The Allies finally regained Burma after a long, horrible campaign.

India. India became an important supply base and training center for Allied forces during World War II. Japan's conquest of Burma in 1942 placed India in great danger. In early 1944, Japanese troops invaded India and encircled the towns of Imphal and Kohima just inside India's border. The British supplied the towns by air. The attackers finally began to withdraw from India late in June. Thousands of Japanese soldiers died of disease and starvation during the retreat.

Closing in on Japan. Superiority at sea and in the air enabled the Allies to close in on Japan in early 1945. By then, Japan had lost much of its empire, most of its aircraft and cargo ships, and nearly all its warships. Hundreds of thousands of Japanese soldiers remained stranded on Pacific islands by-passed by the Allies. American B-29 bombers were pounding Japan's industries, and American submarines were sinking vital supplies headed for Japan.

In January 1945, Major General Curtis E. LeMay took command of the air war against Japan. LeMay ordered more frequent and more daring raids. American bombers increased their accuracy by flying in low during nighttime raids. They began to drop incendiary (fire-producing) bombs that set Japanese cities aflame. A massive incendiary raid in March 1945 destroyed the heart of Tokyo. By the end of the month, about 3 million people in Tokyo were homeless.

Japan's military leaders went on fighting, though they faced certain defeat. The Allies decided they needed more bases to step up the bombing campaign against Japan. They chose the Japanese islands of Iwo Jima and Okinawa.

Iwo Jima lies about 750 miles south of Japan. About 21,000 Japanese troops were stationed there. They prepared to defend the tiny island from fortified caves and underground tunnels. Allied aircraft began bombarding Iwo Jima seven months before the invasion. American marines landed on Feb. 19, 1945, and made slow progress. On February 23 marines raise the American flag on Mount Suribachi but the Japanese hung on desperately until March 16. About 25,000 marines -- about 30 per cent of the landing force -- were killed or wounded in the campaign for Iwo Jima.

Okinawa, the next stop on the Allied route toward Japan, lies about 350 miles southwest of Japan. Allied troops began to pour ashore on Okinawa on April 1, 1945. Japan sent kamikazes to attack the landing force. By the time the battle ended on June 21, kamikazes had sunk at least 30 ships and damaged more than 350 others. The capture of Okinawa cost the Allies about 50,000 casualties. About 110,000 Japanese died, including many civilians who chose to commit suicide rather than be conquered.

By the summer of 1945, some members of Japan's government favored surrender. But others insisted that Japan fight on. The Allies planned to invade Japan in November 1945. American military planners feared that the invasion might cost as many as 1 million U.S. lives. Some Allied leaders believed that Soviet help was needed to defeat Japan, and they had encouraged Stalin to invade Manchuria. However, the Allies found another way to end the war.

The atomic bomb. In 1939, the German-born scientist Albert Einstein had informed President Roosevelt about the possibility of creating a superbomb. It would produce an extremely powerful explosion by splitting the atom. Einstein and other scientists feared that Germany might develop such a bomb first. In 1942, the United States set up the Manhattan Project, a top-secret program to develop an atomic bomb. The first test explosion of an atomic bomb occurred in the New Mexico desert in July 1945.

Roosevelt died in April 1945, and Vice President Harry S. Truman became President of the United States. Truman met with Churchill and Stalin in Potsdam, Germany, in July, shortly after Germany's defeat. At the Potsdam Conference, Truman learned of the successful test explosion of the atomic bomb and informed the other leaders of it. The United States, Britain, and China then issued a statement threatening to destroy Japan unless it surrendered unconditionally. In spite of the warning, Japan went on fighting.

On Aug. 6, 1945, an American B-29 bomber called the Enola Gay dropped the first atomic bomb used in warfare on the Japanese city of Hiroshima. The explosion killed from 70,000 to 100,000 people, it is estimated, and destroyed about 5 square miles. After Japanese leaders failed to respond to the bombing, the United States dropped a larger bomb on Nagasaki on August 9. It killed about 40,000 people. Later, thousands more died of injuries and radiation from the two bombings. Meanwhile, on August 8, the Soviet Union declared war on Japan and invaded Manchuria. Soviet troops raced south toward Korea.

Victory in the Pacific. Although Japan's emperors had traditionally stayed out of politics, Hirohito urged the government to surrender. On August 14, Japan agreed to end the war. Some of the country's military leaders committed suicide.

On Sept. 2, 1945, representatives of Japan signed the official statement of surrender aboard the U.S. battleship Missouri, which lay at anchor in Tokyo Bay. Representatives of all the Allied nations were present. Truman declared September 2 as V-J Day, or Victory over Japan Day. World War II had ended.

Throughout World War II, a secret war was fought between the Allies and the Axis to obtain information about each other's activities and to weaken each other's war effort. Codebreakers tried to decipher secret communications, and spies worked behind enemy lines to gather information. Saboteurs tried to disrupt activities on the home front. Many people in Axis-held territories joined undercover resistance groups that opposed the occupying forces. All the warring nations used propaganda to influence public opinion.

The Ultra secret. Soon after the outbreak of World War II, Britain obtained, with the help of Polish spies, one of the machines Germany used to code secret messages. In an outstanding effort, British mathematicians and codebreakers solved the machine's electronic coding procedures. Britain's ability to read many of Germany's wartime communications was known as the Ultra secret. Ultra helped the Allies defeat Germany.

The Ultra secret played an important role in battle. During the 1940 Battle of Britain, for example, Ultra supplied advance warning of where and when the Luftwaffe planned to attack. Ultra also helped Montgomery defeat the Germans in Egypt in 1942 by providing him with Rommel's battle plan. The British carefully guarded the Ultra secret. They were extremely cautious about using their knowledge so that Germany would not change its coding procedures. The Germans never discovered that Britain had broken their code.

Spies and saboteurs were specially trained by the warring nations. Spies reported on troop movements, defense build-ups, and other developments behind enemy lines. Spies of Allied nations also supplied resistance groups with weapons and explosives. Saboteurs hampered the enemy's war effort in any way they could. For example, they blew up factories and bridges and organized slowdowns in war plants.

Germany had spies in many countries. But its efforts at spying were less successful in general than those of the Allies. The U.S. government set up a wartime agency called the Office of Strategic Services (OSS) to engage in spying and sabotage. The OSS worked closely with a similar British agency, the Special Operations Executive. The Soviet Union operated networks of spies in Allied nations as well as in Germany and Japan.

Resistance groups sprang up in every Axis-occupied country. Resistance began with individual acts of defiance against the occupiers. Gradually, like-minded people banded together and worked in secret to overthrow the invaders. The activities of resistance groups expanded as the war continued. Their work included publishing and distributing illegal newspapers, rescuing Allied aircrews shot down behind enemy lines, gathering information about the enemy, and sabotage.

In such countries as France, Yugoslavia, and Burma, resistance groups engaged in guerrilla warfare. They organized bands of fighters who staged raids, ambushes, and other small attacks against the occupation forces.

All resistance movements suffered many setbacks. But they also achieved outstanding successes. For example, the French resistance interfered with German efforts to turn back the Allied invasion of Normandy in 1944. Norwegian resistance workers destroyed a shipment of heavy water headed for Germany. Heavy water is a substance needed in the production of an atomic bomb. Yugoslavia had the most effective resistance movement of all -- the Partisans. With Allied help, the Partisans drove the Germans out of Yugoslavia in 1944.

Even in Germany itself, a small underground movement opposed the Nazis. In July 1944, a group of German army officers planted a bomb intended to kill Hitler. However, Hitler escaped the explosion with minor injuries. He ordered the plotters arrested and executed.

The risks of joining the resistance were great. A resistance worker caught by the Nazis faced certain death. The Germans sometimes rounded up and executed hundreds of civilians in revenge for an act of sabotage against their occupation forces.

Propaganda. All the warring nations used propaganda to win support for their policies. Governments aimed propaganda at their own people and at the enemy. Radio broadcasts reached the largest audiences. Motion pictures, posters, and cartoons were also used for propaganda purposes.

The Nazis skillfully used propaganda to spread their beliefs. Joseph Goebbels directed Germany's Ministry of Propaganda and Enlightenment, which controlled publications, radio programs, motion pictures, and the arts in Germany and German-occupied Europe. The ministry worked to persuade people of the superiority of German culture and of Germany's right to rule the world. After the war began to go badly for the Axis, the Germans claimed that they were saving the world from the evils of Communism.

Mussolini stirred the Italians with dreams of restoring Italy to the glory of ancient Rome. Italy's propaganda also ridiculed the fighting ability of Allied soldiers.

Japan promised conquered peoples a share in the Greater East Asia Co-Prosperity Sphere, which would unite all eastern Asia under Japanese control. Using the slogan "Asia for the Asians," the Japanese claimed that they were freeing Asia from European rule.

Nightly newscasts beamed by the British Broadcasting Corporation (BBC) to the European mainland provided truthful information about the day's fighting. The Nazis made it a crime for people in Germany and German-held lands to listen to BBC broadcasts.

The U.S. government established the Office of War Information (OWI) to encourage American support for the war effort. The agency told Americans that they were fighting for a better world. In 1942, the Voice of America, a government radio service, began broadcasting to Axis-occupied countries.

The warring countries also engaged in psychological warfare intended to destroy the enemy's will to fight. American planes dropped leaflets over Germany that told of Nazi defeats. The Axis nations employed a few traitors who broadcast radio programs to weaken the morale of Allied soldiers. For example, Mildred Gillars, an American known as "Axis Sally," made broadcasts for Germany. Another American, Iva D'Aquino, who was called "Tokyo Rose," broadcast for Japan. Such broadcasts merely amused most troops.

New opportunities opened up for American blacks during World War II. In 1941, Roosevelt created the Fair Employment Practices Committee to prevent job discrimination in U.S. defense industries. Large numbers of Southern blacks moved to the North to work in war plants.

Mobilizing for the war. The United States introduced its first peacetime draft in September 1940. Under the draft law, all men aged 21 through 35 were required to register for military service. The draft was later extended to men 18 through 44. More than 15 million American men served in the armed forces during World War II. About 10 million were drafted. The rest volunteered. About 338,000 women served in the U.S. armed forces. They worked as mechanics, drivers, clerks, and cooks and also filled many other noncombat positions.

Canada also expanded its armed forces greatly during World War II. At the outbreak of the war, the Canadian government promised not to draft men for service overseas. Canada relied on volunteers for overseas duty until November 1944. By then, it suffered from a severe shortage of troops and began to send draftees overseas. More than a million Canadians, including about 50,000 women, served in the armed forces during the war.

Financing the war. The U.S. and Canadian governments paid for the costs of World War II in several ways. In one major method, they borrowed from individuals and businesses by selling them war bonds, certificates, notes, and stamps. The United States government raised nearly $180 billion from such sales. Canada's government also raised several billion dollars.

Taxes also helped pay for World War II. Income increased tremendously during the war years. As a result, revenue from income taxes soared. In the United States, the tax rate on the highest incomes reached 94 per cent. The government also taxed entertainment and such luxury goods as cosmetics and jewelry. Corporations paid extra taxes on higher-than-normal profits. Canadians also paid increased taxes during the war.

In spite of greater borrowing and higher taxes, the U.S. and Canadian governments spent more than they raised to pay for the war. In the United States, the national debt increased from about $49 billion in 1941 to $259 billion in 1945. Canada's national debt rose from $4 billion in 1939 to $16 billion in 1945.

Government controls over civilian life in the United States and Canada expanded during World War II. In both countries, the national government established various agencies to direct the war effort on the home front. The agencies helped prevent skyrocketing prices, severe shortages, and production foul-ups. The War Production Board, for example, controlled the distribution of raw materials needed by U.S. industries. The Office of Price Administration limited price increases in the United States. It also set up a rationing program to distribute scarce goods fairly. Each family received a book of ration coupons to use for purchases of such items as sugar, meat, butter, and gasoline.

Canada's government had even greater wartime powers. For example, the National Selective Service controlled Canada's work force. It forbade men of military age to hold jobs it termed "nonessential." Such jobs included driving a taxi or selling real estate. Canada's Wartime Prices and Trade Board determined wages and prices and set up a rationing program.

Treatment of enemy aliens. During World War II, the U.S. government classified more than a million newly arrived immigrants from Germany, Italy, and Japan as enemy aliens. However, only the Japanese were treated unjustly. After the bombing of Pearl Harbor, some Americans directed their rage at people of Japanese ancestry. In 1942, anti-Japanese hysteria led the U.S. government to move about 110,000 West Coast residents of Japanese ancestry to inland relocation camps. They lost their homes and their jobs as a result. About two-thirds of them were citizens of the United States. Canada also relocated about 21,000 people of Japanese ancestry during the war.

In Germany, most of the people greeted the start of World War II with little enthusiasm. But Germany's string of easy victories from 1939 to mid-1941 stirred support for the war. By the summer of 1941, the Germans did not expect the war to last much longer.

Civilian life. Food, clothing, and other consumer goods remained plentiful in Germany during the early years of the war. Imports poured in from Nazi-occupied countries of Europe. The Allied bombing of Germany got off to a slow start and did little damage at first.

Germany's situation had changed by late 1942. The armed forces bogged down in the Soviet Union, and there were fewer reports of German victories to cheer the people. Allied bombs rained down day and night on German cities. Consumer goods became scarce. Yet the people continued to work hard for the war effort.

The Nazi terror. Hitler's dreaded secret police, the Gestapo, ruthlessly crushed opposition to the Nazi Party. The Gestapo arrested anyone suspected of opposing Nazism in Germany and in German-held territories.

To free German men for combat, the Gestapo recruited workers from occupied countries. Millions of Europeans were eventually forced to work long hours under terrible conditions in German war plants. Many died of mistreatment or starvation.

The Nazis brutally persecuted several groups, including Jews, Gypsies, and Slavs. By 1942, Hitler had started a campaign to murder all European Jews. The Nazis rounded up Jewish men, women, and children from occupied Europe and shipped them in boxcars to concentration camps. Many Jews were mowed down by firing squads or killed in groups in gas chambers. Others died from lack of food, disease, or torture. Altogether, Hitler's forces killed approximately 6 million European Jews. About 4 million of these people died in concentration camps. The Nazis also slaughtered many Poles, Slavs, Gypsies, and members of other groups.

In other countries, conditions on the home front depended on the nearness of the fighting and on the length of the war effort. Conditions were especially difficult in the Soviet Union, where fierce fighting went on for nearly four years. Stalin ordered retreating Soviet soldiers to burn everything in their path that German troops could use for food or shelter. But that scorched-earth policy also caused great hardships for the Soviet people. Millions of Soviet civilians died of famine and other war-related causes. In Ukraine and areas occupied by the Soviet Union, many of the people at first welcomed the conquering German troops. They believed that the Germans would deliver them from Stalin's harsh rule. But the cruelty of the Nazi occupation forces turned the people against them. During World War II, civilians and soldiers in the Soviet Union fought the Germans with a hatred and determination seldom matched elsewhere in Europe.

The civilian population of Britain also united wholeheartedly behind the war effort. The people worked long hours in war plants and accepted severe shortages of nearly all goods. Prime Minister Churchill inspired the British people with his stirring words.

Life was especially hard in the countries under Nazi rule. Germany looted the conquered lands to feed its own people and fuel its war effort. Opponents of Nazism lived in constant fear of Gestapo brutality.

Japan came closest to collapse of all the warring nations. As the Allies closed in, they deprived Japan of more and more of the raw materials needed by the country's industries. American bombers pounded Japan's cities, and American submarines sank Japanese cargo ships. By 1945, hunger and malnutrition were widespread in Japan. But the Japanese people remained willing to make enormous sacrifices for the war effort.

Deaths and destruction. World War II took more lives and caused more destruction than any other war. Altogether, about 70 million people served in the armed forces of the Allied and Axis nations. About 17 million of them lost their lives. The Soviet Union suffered about 71/2 million battle deaths, more than any other country. The United States and Great Britain had the fewest battle deaths of the major powers. About 400,000 American and about 350,000 British military personnel died in the war. Germany lost about 31/2 million servicemen, and Japan about 11/4 million.

Aerial bombing during World War II rained destruction on civilian as well as military targets. Many cities lay in ruins by the end of the war, especially in Germany and Japan. Bombs wrecked houses, factories, and transportation and communication systems. Land battles also spread destruction over vast areas. After the war, millions of starving and homeless people wandered among the ruins of Europe and Asia.

No one knows how many civilians died as a direct result of World War II. Bombing raids destroyed many of the records needed to estimate those deaths. In addition, millions of people died in fires, of diseases, and of other causes after such essential services as fire fighting and health care broke down in war-torn areas.

The Soviet Union and China suffered the highest toll of civilian deaths during World War II. About 19 million Soviet civilians and as many as 10 million Chinese civilians died. Many of the deaths resulted from famine.

Displaced persons. World War II uprooted millions of people. By the war's end, more than 12 million displaced persons remained in Europe. They included orphans, prisoners of war, survivors of Nazi concentration and slave labor camps, and people who had fled invading armies and war-torn areas. Other people were displaced by changes in national borders. For example, many Germans moved into Poland, Czechoslovakia, and other lands in eastern Europe that the Nazis took over. After the war, those countries expelled these German residents.

To help displaced persons, the Allies established the United Nations Relief and Rehabilitation Administration (UNRRA). UNRRA began operating in 1944 in areas freed by the Allies from Nazi occupation. The organization set up camps for displaced persons and provided them with food, clothing, and medical supplies. By 1947, most of the displaced persons had been resettled. However, about a million people still remained in camps. Many had fled from countries in eastern Europe and refused to return to homelands that had come under Communist rule.

New power struggles arose after World War II ended. The war had exhausted the leading prewar powers of Europe and Asia. Germany and Japan ended the war in complete defeat, and Britain and France were severely weakened. The United States and the Soviet Union emerged as the world's leading powers. Their wartime alliance soon collapsed as the Soviet Union sought to spread Communism in Europe and Asia. The struggle between the Communist world, led by the Soviet Union, and the non-Communist world, led by the United States, became known as the Cold War.

The United States had fought the Axis to preserve democracy. After the war, Americans found it impossible to return to the policy of isolation their country had followed before the war. Americans realized that they needed strong allies, and they helped the war-torn nations recover.

World War II had united the Soviet people behind a great patriotic effort. The Soviet Union came out of the war stronger than ever before, in spite of the severe destruction it had suffered. Before the war ended, the Soviet Union had absorbed three nations along the Baltic Sea -- Estonia, Latvia, and Lithuania. It had also taken parts of Poland, Romania, Finland, and Czechoslovakia by mid-1945. At the end of the war, Soviet troops occupied most of eastern Europe. In March 1946, Churchill warned that an "iron curtain" had descended across Europe, dividing eastern Europe from western Europe. Behind the Iron Curtain, the Soviet Union helped Communist governments take power in Bulgaria, Czechoslovakia, Hungary, Poland, and Romania.

Communism also gained strength in the Far East. The Soviet Union set up a Communist government in North Korea after the war. In China, Mao Zedong's Communist forces battled Chiang Kai-shek's Nationalist armies. Late in 1949, Chiang fled to the island of Taiwan, and China joined the Communist world.

By 1947, Communists threatened to take control of Greece, and the Soviet Union was demanding military bases in Turkey. That year, President Truman announced that the United States would provide military and economic aid to any country threatened by Communism. American aid helped Greece and Turkey resist Communist aggression.

In 1948, the United States set up the Marshall Plan to help war-torn nations in Europe rebuild their economies. Under the plan, 18 nations received $13 billion in food, machinery, and other goods. The Soviet Union forbade countries in eastern Europe to participate in the Marshall Plan.

The nuclear age opened with the development of the atomic bomb during World War II. Many people believed that weapons capable of mass destruction would make war unthinkable in the future. They hoped that the world would learn to live in peace. But a race to develop ever more powerful weapons soon began.

At the end of World War II, only the United States knew how to build an atomic weapon. In 1946, the United States proposed the creation of an international agency that would control atomic energy and ban the production of nuclear weapons. But the Soviet Union objected to an inspection system, and the proposal was dropped. Stalin ordered Soviet scientists to develop an atomic bomb, and they succeeded in 1949. During the early 1950's, the United States and the Soviet Union each tested an even more destructive weapon, the hydrogen bomb.

People have feared a nuclear war since the nuclear age began. At times, Cold War tensions threatened to erupt into war between the two superpowers. But the terrifying destructiveness of nuclear weapons may well have kept them from risking a major war.

Birth of the United Nations (UN). Out of the horror of World War II came efforts to prevent war from ever again engulfing the world. In 1943, representatives of the United States, Great Britain, the Soviet Union, and China met in Moscow. They agreed to establish an international organization that would work to promote peace. The four Allied powers met again in 1944 at Dumbarton Oaks, an estate in Washington, D.C. The delegates decided to call the new organization the United Nations. In April 1945, representatives from 50 nations gathered in San Francisco, Calif., to draft a charter for the United Nations. They signed the charter in June, and it went into effect on October 24.

Peace with Germany. Before World War II ended, the Allies had decided on a military occupation of Germany after its defeat. They divided Germany into four zones, with the United States, the Soviet Union, Great Britain, and France each occupying a zone. The four powers jointly administered Berlin.

At the Potsdam Conference in July 1945, the Allies set forth their occupation policy. They agreed to abolish Germany's armed forces and to outlaw the Nazi Party. Germany lost territory east of the Oder and Neisse rivers. Most of the region went to Poland. The Soviet Union gained the northeastern corner of this territory.

The Allies brought to trial Nazi leaders accused of war crimes. The trials exposed the monstrous evils inflicted by Nazi Germany. Many leading Nazis were sentenced to death. The most important war trials took place in the German city of Nuremberg from 1945 to 1949.

Soon after the occupation began, the Soviet Union stopped cooperating with its Western Allies. It blocked all efforts to reunite Germany. The Western Allies gradually joined their zones into one economic unit. But the Soviet Union forbade its zone to join.

The city of Berlin lay deep within the Soviet zone of Germany. In June 1948, the Soviet Union sought to drive the Western powers from Berlin by blocking all rail, water, and highway routes to the city. For over a year, the Western Allies flew in food, fuel, and other goods to Berlin. The Soviet Union finally lifted the Berlin blockade in May 1949, and the airlift ended in September.

The Western Allies set up political parties in their zones and held elections. In September 1949, the three Western zones were officially combined as the Federal Republic of Germany, also known as West Germany. In May 1955, the Western Allies signed a treaty ending the occupation of West Germany, and granting the country full independence. However, the treaty was not a general peace treaty because the Soviet Union refused to sign it. The Soviet Union set up a Communist government in its zone. In October 1949, the Soviet zone became the German Democratic Republic, also called East Germany.

In September 1990, the Soviet Union and the Western Allies signed a treaty to give up all their occupation rights in East and West Germany. In October 1990, Germany was reunited as a non-Communist nation.

Peace with Japan. The military occupation of Japan began in August 1945. Americans far outnumbered other troops in the occupation forces because of the key role their country had played in defeating Japan. General MacArthur directed the occupation as supreme commander for the Allied nations. He introduced many reforms designed to rid Japan of its military institutions and transform it into a democracy. A Constitution drawn up by MacArthur's staff took effect in 1947. The Constitution transferred all political rights from the Japanese emperor to the people. In addition, the Constitution granted voting rights to women, and denied Japan's right to declare war.

The Allied occupation forces brought to trial 25 Japanese war leaders and government officials who were accused of war crimes. Seven of these individuals were executed. The others received prison sentences.

In September 1951, the United States and most of the other Allied nations signed a peace treaty with Japan. The treaty took away Japan's overseas empire. But it permitted Japan to rearm. The Allied occupation of Japan ended soon after the nations signed the peace treaty. However, a new treaty permitted the United States to keep troops in Japan. China's Nationalist government signed its own peace treaty with Japan in 1952, and the Soviet Union and Japan also signed a separate peace treaty in 1956.

Peace with other countries. Soon after World War II ended, the Allies began to draw up peace treaties with Italy and four other countries that had fought with the Axis -- Bulgaria, Finland, Hungary, and Romania. The treaties limited the armed forces of the defeated countries and required them to pay war damages. The treaties also called for territorial changes. Bulgaria gave up territory to Greece and Yugoslavia. Czechoslovakia gained land from Hungary. Finland lost territory to the Soviet Union. Italy gave up land to France, Yugoslavia, and Greece. The country also lost its empire in Africa. Romania gained territory from Hungary, but in turn it lost land to Bulgaria and the Soviet Union.