The Smith Gun was an ad hoc anti-tank artillery piece used by the British Army and Home Guard during the Second World War. With a German invasion of Great Britain seeming likely after the defeat in the Battle of France, most available weaponry was diverted to the regular British Army, leaving the Home Guard short on supplies, particularly anti-tank weaponry. The Smith Gun was designed by a retired Army Major named William H. Smith as a makeshift anti tank weapon, and was put into production in 1941 following a demonstration to the Prime Minister, Winston Churchill.