Munition

Early in the war, the United Kingdom's munitions industry found itself having difficulty producing the amount of weapons and ammunition needed by the country's armed forces. In response to the crisis, known as the Shell Crisis of 1915, the British government passed the Munitions of War Act in 1915 to increase government oversight and regulation of the industry. The newly created Ministry of Munitions regulated wages, hours and employment conditions in munitions factories. It also forced the factories to admit more women as employees, because so many of the nation's men were engaged in fighting in the war and male labour was in short supply. By June 1917, roughly 80% of the weaponry and ammunition used by the British army during World War I was being made by munitionettes. Notably, women in the industry were paid on average less than half of what the men were paid.

http://www.firstworldwar.com/features/womenww1_four.htm