 Following the Mongol destruction of the Abbasid Caliphate of Baghdad in 1258, two Abbasid princes escaped; Abu al-'Abbas (later known as al-Hakim), was the first to reach Syria under Isa's protection.However, the second surviving prince, Abu al-Qasim (known by the regnal name Al-Mustansir), was chosen by Baybars and inaugurated as the Abbasid caliph in Cairo.Isa accompanied al-Mustansir on his Mamluk-sponsored campaign to reclaim Iraq from the Mongols.