Possible motivations for this complete rebuilding by Al-Adil include the damage the old citadel may have sustained from earthquakes in 1200 and 1201 and the threat that other Ayyubid princes continued to pose toward Al-Adil. The most likely motivation is that the defences of the old citadel became obsolete due to the introduction in the 12th century of the counterweight trebuchet, a siege engine easily capable of reducing thick stone walls to rubble. The new citadel introduced a number of important changes to the defensive system, including higher and thicker walls, a wide moat surrounding the citadel, and numerous closely spaced, high, massive towers. Unlike the older towers, these were square rather than round in design. The towers contained platforms on which trebuchets could be placed. Due to their high position, these trebuchets could outrange enemy artillery and thereby prevent them from breaching the walls.