While the Byzantine Roman and Sassanid Persian empires were both weakened by the Byzantine–Sasanian War of 602–628, a new power in the form of Islam grew in the Middle East under Muhammad in Medina. In a series of rapid Muslim conquests, the Rashidun army, led by the Caliphs and skilled military commanders such as Khalid ibn al-Walid, swept through most of the Middle East, taking more than half of Byzantine territory in the Arab–Byzantine wars and completely engulfing Persia in the Muslim conquest of Persia. It would be the Arab Caliphates of the Middle Ages that would first unify the entire Middle East as a distinct region and create the dominant ethnic identity that persists today. These Caliphates included the Rashidun Caliphate, Umayyad Caliphate, Abbasid Caliphate, and later the Seljuq Empire.