Isolationism was motivated by a number of factors, including:
- The disillusionment with the aftermath of World War I.
- The desire to avoid getting embroiled in future European conflicts.
- The belief that the US was strong enough to defend itself against any threats.
The United States pursued a number of policies to implement its isolationist agenda:
- It refused to join the League of Nations, an international organization created to promote peace and security after World War I.
- It passed a series of neutrality acts in the 1930s, which prohibited the sale of arms to belligerents and restricted American travel on belligerent ships.
- It adopted a policy of non-recognition of the Soviet Union, which was seen as a threat to the American way of life.
American foreign policy changed dramatically in the late 1930s and early 1940s as the threat of Nazi Germany became increasingly clear. The US began to provide assistance to the Allies in the form of lend-lease aid, and in 1941, it entered World War II after the attack on Pearl Harbor.