From the accounts in Ezra and Nehemiah it is certain that only a small minority of Babylonian Jewry returned to rebuild the Land of Israel. The Murashu Tablets, the records of a prominent family of Babylonian bankers which mention numerous Jews, are usually taken as evidence of Jewish business activity in Nippur during the reigns of Artaxerxes I (465/4–424 B.C.E.) and Darius II (423–404 B.C.E.). That Jews attained positions of importance is indicated by the biblical account of Nehemiah, who was a high official of the Persian king, and this state of affairs provides the backdrop for the books of Esther and Daniel.
After Alexander’s conquest of Babylon in 331 B.C.E., Mesopotamia was ruled by the Seleucids for some two centuries. They soon founded new cities, which, together with the garrisons they established, fostered the Hellenization of Babylonia. We have no evidence regarding the effects of this process on the Jewish communities. The privileges accorded to the Jews by the Persians were reconfirmed by the new rulers. In the late third century B.C.E. Jews serving in the Seleucid army were excused from certain duties for religious reasons. One heritage of the Seleucid period in Babylonia was the use of the Seleucid era as a means of counting years (taking 312 B.C.E. as the year 1), a pattern that some Jewish communities continued well into the Middle Ages.
By 129 B.C.E. the decline of Seleucid power made possible the westward expansion of the Parthians (Parthia is located east and north of the Caspian Sea), and Babylonia now came under Parthian rule. The Parthian Empire allowed the native populations to continue their indigenous traditions, leaving the Greek colonies intact and granting favorable treatment to the Jews. Some contacts between the Parthians and the Hasmonean rulers of Palestine must have occurred. We know that in 41/40 B.C.E. the Parthians deposed Herod and supported the Hasmonean Judah Antigonus, only to be chased back across the Euphrates by the Romans in 38 B.C.E.
Little is known of the position of the Jews in the Parthian Empire during the Hellenistic period, but the evidence indicates that the majority of them were farmers and tradesmen with a small upper class of nobility. Attachment to the Land of Israel, especially to Jerusalem, and pilgrimage to the Temple are attested. From the story of the conversion to Judaism (ca. 40 C.E.) of the royal house of Adiabene, a Parthian vassal state in the upper Tigris region, we gather that Jews and Judaism were a regular part of Mesopotamian culture and life in this period. There was even a short-lived Jewish state in Babylonia from about 20 to 35 C.E.