Small pockets of Jews had grown up in various places in the Middle East since at least the early days of the monarchy. Foreign alliances allowed Jewish kings to bargain for power and influence and opened economic doors. With the trade routes came traveling merchants, some of whom decided to relocate. The first major Jewish communities outside of Israel and Judah were the result of the various mass deportations. By the time Cyrus had made a return possible, Mesopotamian communities had been established for over two generations. With the threat of imminent persecution lifted by a tolerant ruler, many Jews simply stayed in Iraq. There they founded thriving cultural and religious institutions, including the academies that went on to produce some of Judaism’s most important legal and theological works. Under successive political regimes with varying policies toward religious pluralism, Iraqi Jews experienced uneven fortunes, but on the whole did much better than merely survive. During the first several centuries of Islamic rule from the capital cities Damascus and Baghdad, Jews enjoyed considerable autonomy and even held high government offices. But after the invasion of the newly Islamized Saljuqid Turks from Central Asia, Jewish life in the Middle East changed dramatically. The Saljuqid Sultan effectively abolished the offices of Exilarchate and Gaonate, which had been the backbone of Jewish autonomy. Meanwhile Jewish communities had grown in Europe since Roman times and had begun to thrive in Germany under Charlemagne. Now many Middle Eastern Jews would look to Europe in hopes of another new start. From the eleventh century until at least the late nineteenth, the center of Judaism would shift from the eastern Mediterranean to central and eastern Europe.