The Medieval Tank
During the wild melee of battle, ranks mixed and battle often time broke down into a series of multiple duels or multi-soldier brawls. This confusion was perfect for a man on horseback with a sharp sword. The beast would cut a wide path and he could wade into almost any part of the battle he wanted and when he did you needed him to be from your camp or all was lost. Covered in mail dealing blows down on a lightly armed man the knight on horseback was like a variable juggernaut and was the equivalent to the tank of the modern era.