The US military has always valued and emphasized the ability of soldiers to march quickly over long distances. Practice marches have been a staple of infantry training whenever training was possible (it hasn't always been compatible with the way volunteers were recruited in the 18th and 19th century) However, as soldiers became more likely to be recruited from urban areas, and mechanization of modern war increased, other training, such as marksmanship, became seen as more important.

This trend sharply reversed itself because of the Korean war experience. In the Korean war, rough terrain and poor roads meant that units relying on motor vehicles lacked mobility. Troops were often not in shape enough to move up steep Korean hillsides and mountains while laden with weapons and heavy packs. After the Korean war, the army made it a point of emphasis to keep soldiers physically fit at all times while on active duty, and subsequent conflicts in rough terrain have only made the need for physical fitness more obvious.