During the Second Crusade the Siege of Damascus began on the 24th of July 1148 and lasted four days. The Crusader army camped to the east of Damascus which was least heavily defended but which lacked a water supply for the besiegers. On the 27th of July Muslim reinforcements arrived led by Nur ad-Din Zangi, and cut the crusader army off from access to the water supply. The crusaders abandoned the siege and retreated back to Jerusalem.