After the Sassanid Empire was conquered by Muslim Arabs in 644, the newly established Rashidun Caliphate designated the Church of the East as an official "dhimmi" minority group headed by the Patriarch of the East.
After the Sassanid Empire was conquered by Muslim Arabs in 644, the Church of the East enjoyed a period of rapid expansion. Syrian and Persian Christians were tolerated by the Muslim rulers of the Rashidun Caliphate, and organized into an official "dhimmi" minority group headed by the Patriarch of the East.