The development of mechanical bomb throwers from early experiments in 1914 to the Leach Catapult and the West Spring Gun. The deployment of the Leach Catapult in Gallipoli and on the Western Front in 1915. The ammunition for the bomb throwers. Rejected by the War Office in early 1915 when they would have been extremely useful, the chapter closes with some successful pneumatic bomb throwers or mortars developed by our Allies.