Several major factors contributed to the crystallization of Karaism as a distinct branch of Judaism, beginning in the eighth century. The spread of Islam and the messianic atmosphere that it created influenced the spirit of the Jews in newly Islamicized countries. The conformity to the Babylonian Talmud enforced on Jews living on the peripheries of the Diaspora opened up the possibility of questioning the right of one Jewish administration to have authoritative control over the entire domain of Jewish Law. Finally, the tolerance of Muslim rulers to religious diversity made it feasible for religious dissenters to declare their independence from the dominant group; however, whereas the Karaites expressed their Opposition to rabbinic authority in the form of messianic asceticism, the content of their beliefs and practices had its foundation in pre-Islamic Judaism.
Karaism eventually spread east to Persia and west to Palestine, Egypt, and Spain. Palestine, in particular, became an important center for Karaites in the tenth century, owing to an emphasis on Avelei Zion (mourners of Zion), who called for a return to Jerusalem. Karaites also settled in Turkey; in the twelfth century Karaites began to move into the Crimea and, later, into Lithuania and Poland.
Karaite settlement in Egypt can be traced back to around the ninth century. Karaites were relatively affluent and influential members of the Jewish community during the first several hundred years of their movement's formai existence. Ketubot (marriage contracts) stipulating the rights of Karaite and Rabbinite partners were found in the Cairo Geniza and provided evidence for the occurrence of "mixed" marriages. During this period, the Rabbinites also adopted certain Karaite practices such as purifying themselves with running water rather than immersion in the mikva, or ritual bath. When Maimonides, a highly regarded Rabbinite religious scholar, came to Cairo in the late twelfth century, he severely admonished the Rabbinites for imitating Karaite customs, and his anti-Karaite polemics prevailed. For the most part, social distance between the two communities continued into the twentieth century, in spite of the fact that Karaites and Rabbinites lived in adjacent quarters in Cairo—Harat al-Yahud and Harat al-Yahud al-Qarain.
The economic position of the Karaites fluctuated with the times, but their political security remained relatively constant until 1956. For example, during Mamluk rule in Egypt (1260-1517), the Karaites were recognized as a distinct group within the Jewish community and fell under the protection of the dhimma, or "People of the Book," as did the Rabbinite Jews. They continued to be granted autonomous status as a religious group under the millet system of the Ottomans and to function, more or less, as an independent religious community until their immigration to Israel in the 1950s. Despite their separate status, however, Egyptian Karaites always regarded themselves and were regarded as Jews by both Rabbinite and Muslim Egyptians.
The majority of the world's Karaites now live in Israel. They came to Israel under the Law of Return (a law that grants automatic citizenship to Jews); they participate in the military and are enrolled in the same educational institutions as Rabbinites. Nevertheless, the Karaites have faced many obstacles to maintaining a distinct identity within Israeli society. These obstacles include discrimination they have encountered as Middle Eastern Jews, the unwillingness of the Chief Rabbinate to recognize or support trends within Judaism that deviate from Orthodoxy, and the influence of secularism. Karaite leaders have taken measures to counter these forces by organizing summer camps, after-school religious instruction, parties for youth, and international conferences to renew and strengthen ties with other Karaite communities, and by publishing a bimonthly bulletin.