With the onset of World War II in December 1941 , the armed forces rapidly swelled in size .
The Army once again became a force of millions , and the need for a self - policing law enforcement system rematerialized .
With the onset of World War II in December 1941 , the armed forces rapidly swelled in size and the Army once again became a force of millions , and the need for a self - policing law enforcement system rematerialized .