The Outbreak of War

The USSR invaded Poland on September 17. Germany and the USSR quickly conquered Poland. In 1940, German armies also moved westward, quickly conquering Belgium, Luxembourg, the Netherlands, and France. European armies seemed to be no match for the Nazi Wehrmacht ("war machine"). The Germans also launched the Battle of Britain, a bombing campaign against London and other targets in England. The Nazis intended to follow this air campaign with an invasion of Britain, but the British withstood the Nazi bombings and shot down more than 1,700 German planes, forcing Hitler to abandon his goal of invading the British isles. In June 1941, Hitler broke the Nazi-Soviet Pact by invading the USSR. By the fall, Nazi troops had advanced deep into the Soviet Union, conquering many Russian cities and nearly reaching the Soviet capital, Moscow.

As war broke out in Europe and Asia in the 1930s, many Americans wanted their nation to avoid becoming involved in the fighting. World War I had led many Americans to embrace isolationism, the belief that the United States should not involve itself in diplomatic or military disputes abroad. As a presidential candidate in both 1936 and 1940, Franklin Roosevelt had vowed to keep the U.S. out of war. Beginning in 1935, the U.S. Congress passed a series of Neutrality Acts, designed to prevent American involvement in foreign wars. The 1937 Neutrality Act prohibited the export of arms to nations that were at war. In the late 1930s, however, Roosevelt increasingly realized that the U.S. would not be able to avoid some role in the war, and began creating policies designed to assist the Allies against the Axis. In 1939, the U.S. began to allow cash and carry arms exports, which allowed other nations to purchase war materials from the U.S. if they paid for them immediately and transported them aboard their own ships. In 1941, the U.S. adopted a policy of Lend-Lease, which enabled the U.S. to sell, lease, or lend supplies to Britain. In 1941, the U.S. and Britain signed the Atlantic Charter, in which the two nations declared their commitment to allowing all nations to determine their own form of government.