It marked the effective end of the isolationist tradition in the United States because for the first time while the country remained officially at peace civilians were drafted into the armed forces to face the possible threat of aggression from abroad.

Why did the US create a peacetime draft?

From 1940 until 1973, during both peacetime and periods of conflict, men were drafted to fill vacancies in the United States Armed Forces that could not be filled through voluntary means.

Why did FDR initiate a peacetime draft?

Roosevelt thought it was important to begin training American men for military service just in case his country was pulled into war. At the time, he thought Great Britain was likely to be the next target and there was little confidence in Great Britain's ability to defeat Germany on its own.