U.S. Army Advantages
During World War II

General Marshall listed a number of clear advantages that the American G.I. had over his German and Japanese counterpart: the M-1 Garand semi-automatic rifle, the jeep and the two-and-a-half ton truck ("Deuce and a half"):

"It is interesting to trace the planning and decisions that gave us the Garand rifle and the tremendous small arms fire-power that went with it, noting especially that the War Department was strenuously opposed."

More about the M-1 Garand rifle can be read here