"If drafted, a man served for twelve months. According to the Burke-Wadsworth Act's provisions, drafted soldiers had to remain in the Western Hemisphere or in United States possessions or territories located in other parts of the world. The act provided that not more than 900,000 men were to be in training at any one time, and it limited service to 12 months."
In mid-1941, Congress extended the period of service beyond 12 months and the president agreed to that. There was some grumbling, but no widespread desertions, and after December 7 of that year, the grumbling stopped.