The US "solved" that particular problem by keeping its army much smaller than it could've been, precisely to free up more healthy 18 year olds for factory jobs.

The US "solved" that particular problem by keeping its army much smaller than it could've been, precisely to free up more healthy 18 year olds for factory jobs. Between the British Empire, the various Chinese governments and Soviet Union, the Allies had plenty of manpower, but all that was meaningless without US munitions, US equipment, US food, and US ships to get them where they were needed.