First World War munitions factory. Artillery guns and their mounts being constructed at a US munitions factory during the First World War (1914-1918). The guns seen here range in size from 6-inch guns (foreground) to parts for 10, 12 and 14-inch guns (background). The measurements refer to the diameter of the shells fired by the guns. Huge numbers of artillery shells were used in the trench warfare on the Western Front, killing millions on all sides but failing to break the stalemate. The USA initially supplied Britain and France with munitions and other essential supplies, and then entered the war itself on 6 April 1917. Photographed in 1918 at the Bethlehem Steel Company, Pennsylvania, USA.