The founder of Islam and ruler of the Arab peninsula Muhammad died in June of 632, without a clear successor to his spiritual and military empire. Muhammad’s four sons had died in infancy and two of his daughters had died as young women. Only Fatimah survived him and only she carried on his line. Many of his followers supported his longtime friend Abu Bakr, the father of his young wife Aisha, who had given Muhammad aid when he was persecuted by the Meccans for his preaching, and had remained by the Prophet’s side ever since. Others felt that rule of the Arab peninsula and the Muslim faith ought to go to Muhammad’s closest male relative, his first cousin and Fatimah’s husband Ali.
This schism could have led to war between the two men, but for Ali’s decision to accept Abu Bakr as first Caliph, and serve as his sometime advisor. That is not to suggest there was no conflict between them. Abu Bakr denied Fatimah lands at Khaybar she felt her father Muhammad had left her as inheritance. Shi’a followers, who believe Islam’s charge should stay in the House of the Prophet, still assert that Abu Bakr was responsible for the intentional burning of Ali and Fatima’s house. But Ali was not the source of Abu Bakr’s strife.
Everyone else was. After Muhammad’s death, no less than three other men claimed to be the new Prophet of Islam, and started preaching and trying to gain followers and fighters. Apostasy and rebellion quickly spread. Wars to put down the self proclaimed prophets, wars of retribution against the Sassanid Persians, wars of expansion, and wars just because they were in the habit now took over until the Muslims dominated one of the largest empires in world history. The Sassanids were conquered by 654.
What did this mean for religious minorities like Jews, Christians, and Zoroastrians? Living under Arab Muslim rule meant all the usual indignities of living under conquest. In the first hundred years it did not include much forced conversion, in contrast with Christianity particularly Byzantine and Roman forms. The Muslims referred to non Muslims as dhimmi or “protected”, and charged able bodied men of military age an exemption tax if they did not want to fight in Islam’s holy wars. But they also could go fight, and gain in the booty. Freedom of religion was relative.
The rights of dhimmis were enumerated in an apocryphal pledge between the second caliphate Umar and Christians of Syria, Mesopotamia, or Jerusalem, the Pact of Umar. There are several versions of this and their exact authenticity is uncertain. The rights and responsibilities of a dhimmi were to always show deference to a Muslim: Jewish homes must be built lower; Jewish doors should be so low they must bow to remember their low place. Jews must give up their seat to a Muslim. Passover celebrations were banned. There were not many forced conversions, but free open worship was not tolerated either.