 Following the Roman–Persian Wars and the Byzantine–Sassanid Wars deep-rooted differences between Iraq (formerly under the Persian Sassanid Empire) and Syria (formerly under the Byzantine Empire) also existed.Each wanted the capital of the newly established Islamic State to be in their area.As Uthman ibn Affan became very old, Marwan I, a relative of Muawiyah, slipped into the vacuum, becoming his secretary and slowly assuming more control.