 Complete the following phrase:  In 1144, Zengi conquered Edessa, a crusader stronghold, which led to a new crusade from Europe in 1148. In the meantime Zengi was assassinated and his territory was divided among his sons, one of whom, Nur ad-Din, emir of Aleppo, made an alliance with Damascus. When the European crusaders arrived, they and the nobles of Jerusalem agreed to attack Damascus. 