Umar was the second Rashidun Caliph and reigned during 634-644. Umar's caliphate is notable for its vast conquests, aided by brilliant field commanders, he was able to incorporate present day Iraq, Iran, Azerbaijan, Armenia, Georgia, Syria, Jordan, Palestine, Lebanon, Israel, Egypt, and part of Afghanistan, Turkmenistan and south western Pakistan into the empire of the Muslims. All of these were permanent conquests. The Byzantines lost more then three form of their territory and in Persia, the Sassanid empire ceased to exist [1].
- ^ A Restatement of the History of Islam and Muslims on Al-Islam.org [1]