The Sassanids were kings of Iran from 224 - 651 A.D. At its greatest extent, their empire stretched from Syria to India, and from Iberia to the Persian Gulf. Major campaigns were launched against them by the Romans, including the emperor Valerian who was defeated and captures (A.D. 260) by Sapor I. A characteristic of Sassanid ideology was the development of the idea of "Iran” with its own political and cultural identity. Their empire came to an end when the Arabs conquered Mesopotamia and Iran.