CALIPHATE. The history of the Muhammadan rulers in the East who bore the title of caliph (q.v.) falls naturally into three main divisions :—(a) The first f our caliphs, the immediate succes sors of Muhammad; (b) The Umayyad caliphs; (c) The Abbasid caliphs. To these three groups the present article is confined ; for the Western caliphs, see SPAIN : History (and minor articles such aS ALMOHADES, ALMORAVIDES) ; for the Egyptian caliphs, see EGYPT: History (§Muhammadan) and FATIMITES. The history of Arabia proper will be found under ARABIA : History.