Printed in the U.S. Army Infantry Drill Manual of 1911 was this black and white diagram depicting the breach of the 1903 Springfield rifle, with all parts named. This rifle was the primary weapon for American troops during World War One and was in use by that army up until 1936. At the time of America's entry into the First World War, April 1917, there were roughly 843,239 Springfield '03 rifles issued; seeing that this was not nearly enough for such an adventure the Springfield Armory manufactured 265,620 additional rifles. In some photographs from the war, American soldiers and Marines are pictured shouldering the British Enfield rifle, which had been modified to fit the ammunition of the Springfield '03. Subsequent modifications produced the Springfield 1903A3 and A4 which were issued to American snipers up until the earlier years of the Vietnam War.