In just over a hundred years--from the death of the Mohammed in 632 to the beginning of the Abbasid Caliphate in 750--the followers of the Prophet swept across the whole of the Middle East, North Africa, and Spain. The conquered territory was larger than the Roman Empire at its greatest expansion, and it was claimed for the Arabs in roughly half the time. How they were able to engulf so many empires, states, and armies in such a short period of time...