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World War II: 1939–1952



September 1939 saw the outbreak of World War II in Europe. Alarmed by the conflict, the United States nevertheless remained a neutral power. While staying out of the war, President Roosevelt found ways to provide U.S. allies with weapons to fight off German invasion. The United States was drawn into the war when Japan bombed Pearl Harbor, Hawaii, on December 7, 1941. For the next three and a half years, the Allies fought for control of the Atlantic, Europe, and the islands of the Pacific. Germany and Japan were finally defeated in 1945. Although fighting ceased in 1945, it took until 1952 for an authorized peace treaty with Japan to be signed and formally acknowledged. World War II was at last officially over. The conflict had caused staggering losses, with estimates ranging from 50 to 80 million people.

At A Glance

  • President Franklin Roosevelt attempted to remain neutral when World War II broke out in Europe in 1939. Wanting to assist its allies, the United States did provide aid through "cash-and-carry" and the Lend-Lease Act.
  • Japan's decision to bomb the U.S. naval base at Pearl Harbor, Hawaii, on December 7, 1941, triggered the United States' entry into World War II.
  • As American men left for the front, six million women stepped out of their traditional roles and into the workforce. There they filled jobs in factories and in the armed forces to support the war effort.
  • Minorities played an integral role in the war effort, serving in the armed forces and supporting the war at home. African Americans in particular worked toward victory in the hope of achieving equal rights.
  • In 1942 Franklin Roosevelt's Executive Order 9066 led to the roundup and internment of nearly 120,000 Japanese-born U.S. citizens and Japanese Americans living on the West Coast.
  • U.S. and Allied forces fought Axis powers in the European Theater from 1942 to 1945. Key battles in North Africa, the Mediterranean, the Soviet Union, and Germany determined the course of the war.
  • The Big Three's discussion at the Yalta Conference determined the fate of Germany. With Germany's surrender in May 1945 came the end of the war in Europe. V-E Day celebrations erupted around the globe.
  • In the Pacific Theater, the United States outmaneuvered Japan by adopting a leapfrog strategy for capturing and defending strategic islands.
  • After Japan's refusal to surrender, President Truman ordered the dropping of atomic bombs on Hiroshima and Nagasaki—devastating the empire and convincing its emperor to concede defeat.
  • Following Japan's surrender Allied powers occupied the country, enacting a wide variety of political, military, social, and economic reforms under the watchful eye of U.S. General Douglas MacArthur.