Mills Bomb hand grenade
The WWI “Mills Bomb” was designed in 1915 by William Mills, a British inventor, for use during the Great War. The design relied upon a spring-loaded external lever and plunger, which would drop and ignite the internal charge when the safety ring was removed and the lever lifted. Early models were manufactured with 7-second time delays, while later versions featured 4-second delays. Due to U.S. grenade design problems, American servicemen relied on French and British designs, such as the “Mills Bomb,” as the primary Allied hand and rifle grenades of the war.