Caliph is the title of Islamic head of state as well as the teaching post of Islam, so it is the title of unified head of state and religious leader when politics and religion are integrated. For example, the four caliphs of the Arab Empire.

Sudan should be a local governor and an army commander at the earliest. Later, after the split of the Islamic world, local political forces claimed the title of king by themselves, thus becoming the first name in the military and political circles. Such as Turkish Sudan, Egyptian Sudan and Sultans Of Brunei.

There is a poem in the Koran that says, "I will definitely set up an agent on the earth." Muhammad and other prophets before him are considered as the agents and rulers of God on the earth. After Muhammad's death, the "caliph" was used to refer to Muhammad's successor, the leader of Muslim community organizations.

The female sultan is called "Sultana", but it is rare in Islamic history. In addition, there is a special Sulu Sultanate. The official ruler of this country is a male sultan, but his wife is actually a "supervisor".

When the prophet Muhammad was alive, he left neither a son nor a clear heir. Therefore, after his death, the heir became the primary problem faced by all Muslims, which led to fierce competition. Umar (the second caliphate), a follower of the prophet, took the initiative to recognize Abu Birkel's caliphate status, thus ending the power struggle and beginning four caliphate periods.