Siege tower

A siege tower is a specialized [siege engine]?, constructed to protect assailants and ladders whilst approaching the defensive wall?s of a fortification?. The tower was often rectangular with four wheels and a height roughly equivalent with the wall or sometimes higher to allow archer?s to stand on top of the tower and fire into the fortification.

Used throughout antiquity in both the far east and Europe, siege towers were of unwieldy dimensions and therefore mostly constructed on site of the siege. Taking a lot of time to construct, siege towers were mainly constructed if the defense of the opposing fortification could not be overcome by ladder assault, by sapping? or by breaching walls or gates.