Crude forms of chemical weapons have been used in warfare for thousands of years – think boiling tar in medieval times. But World War I marked the first use of modern chemical weapons, notably chlorine and mustard gas. The Germans employed them first, but many of the major combatants enlisted chemical agents over the course of the war. The conflict also saw the widespread use of other forms of industrialized warfare that have forever changed how nations fight: tanks, flamethrowers, machine guns, planes, submarine fleets.
Courtesy of National World War I Museum, Kansas City, Missouri
