After mail was sorted and distributed to army units, it still had to get to soldiers out in the field. The large number of letters and small packages required a durable bag. Official mail bags were made from heavy canvas. This one is a burlap sack. Marked US MAIL, it was for temporary use near the front lines and likely abandoned where is was last used. Found in 1st Infantry Division trenches near Laufenburg Castle outside of Aachen, Germany.