Tank
Tanks became a main weapon during World War II, when the German Army introduced a way of using them called Blitzkrieg.  Battles between great numbers of tanks were fought, especially between the Germans and the Soviet Union. The Battle of Kursk was the biggest. Well-known World War II tanks were the German Panzer IV, Panther and Tiger I, Soviet T-34 (made in the largest numbers of any tank of the war and second most ever), the British Matilda, Churchill and Cromwell, and the American M4 sherman (second most produced tank of the war) and Stuart tanks.  There were plans for much larger and more heavily armoured tanks such as the Maus but they were determined to be of little use.  Their huge weight would have made moving them very difficult, and their huge size would have made them easy targets for heavy artillery.