The Tank, Infantry, Mk IV (A22) was a heavy British infantry tank used in the Second World War, best known for its heavy armour, large longitudinal chassis with all-around tracks with multiple bogies, and its use as the basis of many specialist vehicles. It was one of the heaviest allied tanks of the war. This series of tanks was named after Winston Churchill, who was Prime Minister of the United Kingdom and Minister of Defence at the time, and had been involved with the development of the tank as a weapon during the First World War.