World War II and the Early Cold War

When war broke out in Europe in 1939, most Americans wanted to stay out, but Franklin D. Roosevelt sent aid to Britain through Lend-Lease. Japan’s attack on Pearl Harbor on December 7, 1941, brought the nation into World War II. Americans fought from North Africa and Normandy to Iwo Jima and Okinawa; at home, factories armed the Allies, unemployment vanished, and millions of women went to work. The war also brought the mass incarceration of Japanese Americans under Executive Order 9066, upheld in Korematsu v. United States and carried out at camps such as Manzanar. The war ended in 1945 after the atomic bombings of Hiroshima and Nagasaki.

President Harry S. Truman helped found the United Nations, but the wartime alliance with the Soviet Union collapsed into the Cold War. The United States committed itself to containing communism through the Truman Doctrine, the Marshall Plan, the Berlin Airlift, and NATO, and fought the Korean War. Fear of subversion fed the Red Scare and McCarthyism.

At home, the G.I. Bill sent millions of veterans to college and helped them buy homes, fueling postwar prosperity — though Black veterans were often shut out. Black Americans, who had fought for “Double Victory” over fascism abroad and racism at home, pressed for change; Truman desegregated the armed forces in 1948, and by the mid-1950s a new civil rights movement was rising.