00  Islamic conquest of Persia  Since the 0st century BC, the Romans and Parthians had waged a number of wars that lasted for the centuries. In fact these military campaigns outlasted the empires themselves. Both the Roman and Parthian Empires reformed and were replaced by the Byzantine and Sassanid Empires, respectively. These two new superpowers continued their territorial disputes and military confrontations for centuries. But the Sassanids and Byzantines also had various proxy wars, in which they attempted to start rebellions in the opponent's holdings. One example of this was the Byzantine client state the Ghassanids and the Sassanid client state the Lakhmids. These client states served as a buffer zone against the SouthernArab raiders. And both these client states were Arab in origin, but the Ghassanids were Chris