 Complete the following phrase:  Ismat ad-Din is a laqab the descriptive part of an Arabic name meaning purity of the faith; Khatun is an honorific meaning lady or noblewoman. Her given name ism in Arabic is unknown. Her father became regent of Damascus in 1138, and ruled the city on behalf of a series of young emirs of the Burid dynasty. During this time, Damascus chief rivals to the north, Aleppo and Mosul, were united under the rule of the Zengid dynasty. Damascus had maintained an unsteady alliance with the Crusader Kingdom of Jerusalem, but in 1147, Muin ad-Din negotiated an alliance with the Zengid emir of Aleppo, Nur ad-Din, who married Ismat ad-Din as part of the agreement. The next year, forces of Second Crusade conducted the unsuccessful 