of Jewish refugees in Babylon. In the continuous Roman–Persian Wars, the Jews had every reason to hate the Romans, the destroyers of their sanctuary, and to side with the Parthians, their protectors. Possibly it was recognition of services thus rendered by the Jews of Babylonia, and by the Davidic house especially, that induced the Parthian kings to elevate the princes of the Exile, who until then had been little more than mere collectors of revenue, to the dignity of real princes, called Resh Galuta. Thus, then, the numerous Jewish subjects were provided with a central authority which assured an undisturbed development of their own internal affairs. Sasanian period A new ruling family from an ancient dynasty of Iranian priests took control of the region around 223 CE and imposed a new system of government based on Zoroastrianism and local Iranian identity, which often suppressed dissident factions and heterodox views. It dominated the area until the Muslim conquest in the seventh century CE and became known as the Sasanian Empire. The Babylonian Talmud was written during this time and is a source of information for the political, religious, social, and linguistic facets of the empire. Under the Sasanians, Babylonia became the province of Asoristan, with its main city, Ctesiphon, becoming the capital of the Empire. Although there were some tensions between the Jewish community and Zoroastrian priests who sought to unify the entire empire under one religion and were less tolerant than their forebears during the early Sasanian era, the Jewish community's stature and their religious and communal autonomy were generally maintained. The Jewish communities in Mesopotamia flourished, particularly in the fourth century CE, as a result of Shapur's tolerant rule and the Christianization of the Roman Empire, which led to a large Jewish migration from Roman-controlled territory into the only Roman-independent region, the Sasanian Empire. While occasionally there were disputes between Jews and the authorities, the Talmudic texts mainly show respect for the Sasanian government, and the Amora Samuel of Nehardea's remark - "dina demalchuta dina" (The law of the kingdom, the governing empire, must be upheld) reflects this attitude. Shapur I (Shvor Malka, which is the Aramaic form of the name) was a friend to the Jews. His friendship with Shmuel gained many advantages for the Jewish community. Shapur II's mother was Jewish, and this gave the Jewish community a relative freedom of religion and many advantages. Shapur was