1258 saw the conquest of Baghdad and the execution of Abbasid caliph al-Musta'sim by Mongol forces under Hulagu Khan. A surviving member of the Abbasid House was installed as Caliph at Cairo under the patronage of the Mamluk Sultanate three years later; however, the authority of this line of Caliphs was confined to ceremonial and religious matters, and later Muslim historians referred to it as a "shadow" Caliphate.