The attached illustration shows the U.S. Army olive drab flannel pull-over shirt that was first issued to U.S. enlisted men in 1912. This pull-over shirt was produced for the Army up until 1934, when the full button-front shirt was issued.
US Army Shirt WW 1US Army Shirt WW1US Army Shirt World War OneOlive Drab Wool Army Shirt EM Illustration