After the death of the Prophet Muhammad in 632, Arab armies under the early caliphates expanded with remarkable speed, defeating the Byzantine and Sasanian empires and within roughly a century controlling territory from the Iberian peninsula across North Africa and the Levant to Persia and Central Asia. The conquests spread Islam, the Arabic language and a shared administrative and legal culture across this vast zone. Rather than only seizing existing cities, the conquerors founded new garrison settlements (amsar) such as Kufa, Basra and Fustat to house their forces. These often grew into major centres of population and trade.
The garrison towns matured into great cities and seeded a distinctive Islamic urban form organised around the congregational mosque, the suq (market) and residential quarters, a pattern reproduced across the Islamic world.