Illustration of the Shirt Worn by the
American Soldier During W.W. I

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 was produced for the Army up until 1934, when the full button-front shirt was issued. The image above depicts one of the better books you can find concerning the equipment and uniforms of the A.E.F. - the image serves as a link to it's sale page on Amazon.