Muhammad had been established as the supreme overlord and preceptor of all Arabia. It is believed that he did not nominate a successor, and that Abu Bakr was elected as the successor to the Prophet. Abu Bakr was the Caliph or Commander of the Faithful for only two years.
He was succeeded by Umar. Umar was a bold and courageous man. The boundaries of the Islamic State expanded far and wide during his tenure as caliph. Umar was assassinated after ten years as Caliph, and Usman was elected as the third Caliph. When Usman was assassinated after twelve years, he was succeeded by Ali, the son-in-law of the Prophet.
The election of the first four Caliphs, who are known as Khulfai-in-Rashidain (the rightly-guided Caliphs) was real and democratic. Ali was Caliph for five years, after which he expired. After Ali’s death, his son, Hasan, resigned in favour of Muavia, the founder of the Ummayad dynasty. Hasan was, however, murdered.
The followers of Ali, known as the Shiat-i-Ali, (the party of Ali) persuaded Husain, the second son of Ali, to revolt against the son of Muavia. Husain died fighting, after great suffering in Kerbala. Therefore, the rift between the Sunnis and the Shias broadened. The Shias were the supporters of Ali and opposed the Sunnis.
The scene of power now shifted from Mecca to Damascus, when Muavia made it his capital. When the Ummayads became rulers, the Caliphate became a regular kingship, and vices (like the tribal rivalry of earlierdays) again crept in.
The Ummayad was overthrown by the Abbasids, who donned the mantle of the Prophet, by claiming descent from Abbas, the uncle of the Prophet. The Abbasid Caliphate lasted for five centuries and collapasfid in 1258. A.D., when the Mongols plundered Baghdad.
The Caliphate then shifted to Cairo, where Sultan Baibars invited Abul Kasim Ahmed, who had escaped death at the hands of the Mongols, to hold spiritual power. This Caliphate lasted for two-and-a- half centuries.
In the fifteenth century, the Ottomans of Turkey had become a force to contend with. They overthrew the Mameluke Sultans of Egypt, and got the Caliphate transferred to themselves by a deed of assignment. Thus, the Caliphate shifted from Cairo to Constantinople. In 1922, Mustafa Kamal Pasha abolished the Sultanate of Turkey, when he established the Turkish Republic. Two years later, the Caliphate was formally abolished by the National Assembly of the Turkish Republic.