Isolationism means a nation does not join alliances or does not get involved in global situations.
World War II didn't start because of isolationism. But the isolationism of the United States affected the course of war by Great Britain and France not being able to defend their country.
In 1939, World War II started, but the United Sates was not involved. Germany took over Austria and Czechoslovakia. France and Great Britian didn't do anything to prevent this.
During the years of 1934-1937, there was a high tide of isolationism. In America President Roosevelt felt hopeless, because of the worldwide drift towards war. President Roosevelt said to William Bullitt "these may be the last days of...peace before a long chaos."
The U.S. was the most powerful nation in the world after World War I. They had the ability to have other nations "follow rules" like a police officer . But the U.S. practiced isolationism after World War I. They didn't want to get involved in any war involving other nations. They wanted to remain isolated. To a dictator like Adolf Hitler, this was another reason why he decided to practice imperialism. It is similar to a burglar who tries to break in to people's homes. If he knows the police won't watch him and try to arrest him, they will keep on trying to break in to the next home. This is how isolationism is related to World War II.
To keep peace in the world, it is helpful to have someone enforce the rules of fairness and respect. We have an organization called the United Nations who in some ways tries to do that today.
Souces: World War II Workshop-by Mr. Darrel Galera on October 21,2000 at Kapaa Middle School.
World War II by Tom McGowen