Narratives by the medieval sources about Abd al-Malik's motivations in building the Dome of the Rock vary. At the time of its construction, the Caliph was engaged in war with Christian Byzantium and its Syrian Christian allies on the one hand and with the rival caliph Abd Allah ibn al-Zubayr, who controlled Mecca, the annual destination of Muslim pilgrimage, on the other hand. Thus, one series of explanations was that Abd al-Malik intended for the Dome of the Rock to be a religious monument of victory over the Christians that would distinguish Islam's uniqueness within the common Abrahamic religious setting of Jerusalem, home of the two older Abrahamic faiths, Judaism and Christianity. The historian Shelomo Dov Goitein has argued that the Dome of the Rock was intended to compete with the many fine buildings of worship of other religions: "The very form of a rotunda, given to the "Qubbat as-Sakhra", although it was foreign to Islam, was destined to rival the many Christian domes."