When Did the US Join World War II?

The World War II Memorial in Washington, DC.
The World War II Memorial in Washington, DC.

World War II, fought between 1939 and 1945, is considered the largest armed conflict in human history. It fought in six continents and over all the oceans, resulting in over 50 million deaths including the 6 million Jews who were killed in the Holocaust. World War II pitted the Allies against the Axis. The Allies include the US, Soviet Union, and Great Britain while the Axis included Germany, Italy, and Japan. The root causes of the war were the military ideologies and the expansion policies of the Axis groups. The weak response by certain European democracies to the fascist aggression and the non-involvement of the Americans initially gave the Axis power an upper hand in the war.

US Entry Into the War

At the beginning of the war, the United States remained politically neutral and did not appear to support any group. However, President Franklin D. Roosevelt was doing everything possible to make his country prepared for what he considered an inevitable involvement in the conflict. He felt that his country’s security was threatened by the war and decided to provide assistance to the Allies without formally taking part in the war. In November 1939, President Roosevelt persuaded the Congress to review the arms embargo that had been included in the neutrality law to allow for the selling of arms to Britain and France. Fearing that the British would surrender following the fall of France in June 1940, the president pushed for a major military reorganization and began providing assistance to the British in the form of the Lend-Lease. In this arrangement, the US would lend supplies to the British and the payment would be differed.

Pearl Harbor

The US official entry to the war came as a result of the bombing of the American fleet in Pearl Harbor, Hawaii on December 7, 1941. The US was carrying out a successful embargo against the Japanese at the time. During this period, the Japanese closed in on China, forcing them to seek war supplies from the US. In 1940 and 1941, the US government extended support to the Chinese to purchase war equipment and began tightening restrictions against the Japanese. The Japanese imported about 90% of oil from the US and became desperate when the embargo was put in place. They felt that the lack of oil would paralyze their involvement in the war. Refusing the US demand to stop the attack on China, they felt that war with America was becoming increasingly inevitable. Their strategy was to strike first and picked on the American fleet in Pearl Harbor. The following day (December 8, 1941), after the bombing of the fleet, the Americans declared war on Japan, marking their formal entry into World War II. It entered into an agreement with China to fight the Japanese. Soon after, Germany decided to support its ally and also attacked the US. The Americans faced war both in Asia and Europe.


More in World Facts