CALIPHATE'S LAST YEAR (1923 PHOTOS of ISTANBUL) The term Caliphate/Hilafet (from the Arabic خلافة or khilāfa) refers to the first & only system of governance established in Islam, and represented the political authority and unity of the Muslim Ummah. It was initially led by Prophet Muhammad's [PBUH] disciples as a continuation of the political authority the prophet established, known as the 'Rashidun Caliphate'. It represented the unity of the Muslim Ummah, and was the world's first major welfare state. A "caliphate" is also a state which implements such a government. The caliph, or head of state, was often known as Amir al-Mu'minin (أمير المؤمنين "Commander of the Believers". Prophet Muhammad [PBUH] established his capital in Medina, and after he died Medina remained the capital for the rashidun period. The first Caliph to be called Amir al-Mu'minin was Abu Bakr Siddique and then Umar ibn al-Khattāb, the second of the Four Rightly Guided Caliphs. Uthman ibn Affan and Ali ibn Abi Talib also were called by the same title. After the first four caliphs, the Caliphate was claimed by the Umayyads, the Abbasids, and the Ottomans, and for relatively short periods by others, in al-Andalus, North Africa, and Egypt. Mustafa Kemal Atatürk officially abolished the last Caliphate, the Ottoman Empire, and founded the Republic of Turkey, in 1924.