In 1940, with tensions around the world increasing, more than thirty one million young men were required to register for the draft. Most of those drafted were never in actual combat, they supported the front lines in various positions. Their jobs were matched with their skills, so that mechanics maintained army vehicles, cooks fed the soldiers, doctors treated the ill, and engineers built bridges. For every soldier on the front line there were three soldiers supporting him.

There were many different engineer battalions and all played key roles in the effort to support the front lines.

There were many different combat engineer battalions: aviation regiments-these men built and maintained air bases; bridge units-these men built bridges working from pontoons; general service regiments-these troops maintained, constructed, and repaired equipment; and last the special service regiments-these troops were specialists in operating heavy machinery, graphing topography, supplying clean water, and maintaining railways.

Another special force, similar to the army's combat engineer battalions, was the Navy Seabees. Seabees were the worker bees for the navy, as they had the skills to construct airfields, build roads, and harbors.