Before revision: During his reign, the Byzantines lost more than three fourths of their territory and in Persia, and Umar was the king (ruler) of the Sassanid Empire before it ceased to exist .A Restatement of the History of Islam and Muslims on Al-Islam.org Historians estimate more than 4,050 cities were conquered during the reign of Umar.
After revision: During his reign, the Byzantines lost more than three fourths of their territory and in Persia, Umar became the king (ruler) of Iran after the fall of the Sassanid Empire .A Restatement of the History of Islam and Muslims on Al-Islam.org Historians estimate more than 4,050 cities were conquered during the reign of Umar.