From 138 B.C. until the coming of Islam in 636/37 A.D., Mesopotamia is dominated first by the Parthian and then Sasanian empires from Iran. Their strength and wealth is based on control of the trade routes through the region, which connect the cultures of East and West. This often brings the rulers of Mesopotamia into conflict with the expansionist aims of Rome and, later, Byzantium. By the second century A.D., the archetypal Mesopotamian writing system, cuneiform, is almost extinct and has been replaced by alphabetic scripts.