The Rashidun Caliphate was the first of the Islamic Caliphates to rise to power in Arabia, and after the battles of Qadisiya and Nehavend, Persia too. A success in its time, the opportunity left at the battle of Yarmuk was one that they failed to pick up on, resulting in the Byzantines being able to restore their position in the Levant and establish an unassailable front.