Each people was permitted to carry back with it its ancestral gods. The Jews alone had no images to take; the sacred vessels of the temple of Jerusalem were accordingly given to them. It was a faithful remnant that returned to the land of their fathers, consisting mostly of priests and Levites, determined henceforward to obey strictly the laws of their God, and full of gratitude to their deliverer. In Jerusalem Cyrus thus had a colony whose loyalty to himself and his successors could be trusted, and who would form, as it were, an outpost against attacks on the side of Egypt.

As long as Cyrus and his son Kambyses lived Babylonia also was tranquil. They flattered the religious and political prejudices of their Babylonian subjects, and the priesthood saw in them the successors of a Sargon of Akkad. But with the death of Kambyses came a change. The new rulers of the empire of Cyrus were Persians, proud of their nationality and zealous for their Zoroastrian faith. They had no reverence for Bel, no belief in the claim of Babylon to confer a title of legitimacy on the sovereign of western Asia. The Babylonian priesthood chafed, the Babylonian people broke into revolt. In October B.C. 521 a pretender appeared who took the name of Nebuchadrezzar II., and reigned for nearly a year. But after two defeats in the field, he was captured in Babylon by Darius and put to death in August 520. Once more, in B.C. 514, another revolt took place under a second pretender to the name of "Nebuchadrezzar the son of Nabonidos." The strong walls of Babylon resisted the Persian army for more than a year, and the city was at last taken by stratagem. The walls were partially destroyed, but this did not prevent a third rebellion in the reign of Xerxes, while the Persian monarch was absent in Greece. On this occasion, however, it was soon crushed, and Ê-Sagila, the temple of Bel, was laid in ruins. But a later generation restored once more the ancient sanctuary of Merodach, at all events in part, and services in honour of Bel continued to be held there down to the time when Babylon was superseded by the Greek town of Seleucia, and the city of Nebuchadrezzar became a waste of shapeless mounds.

Babylonian religion was a mixture of Sumerian and Semitic elements. The primitive Sumerian had believed in a sort of animism. Each object had its zi or "spirit," like men and beasts; the zi gave it its personality, and endowed it, as it were, with vital force. The zi corresponded with the ka or "double" of the Egyptians, which accompanied like a shadow all things in heaven and earth. The gods themselves had each his zi; it was this alone that made them permanent and personal. With such a form of religion there could be neither deities nor priests in the usual sense of the words. The place of the priest was taken by the sorcerer, who knew the spells that could avert the malevolence of the "spirits" or bring down their blessings upon mankind.

With the progress of civilisation, certain of the "spirits" emerged above the rest, and became veritable gods. The "spirit" of heaven became Ana of Erech, the Sky-god; the "spirit" of earth passed into El-lil of Nippur; and the "spirit" of the deep into Ea of Eridu. The change was hastened by contact with the Semite. The Semite brought with him a new religious conception. He believed in a god who revealed himself in the sun, and whom he addressed as Baal or "Lord." By the side of Baal stood his colourless reflection, the goddess Baalath, who owed her existence partly to the feminine gender possessed by the Semitic languages, partly to the analogy of the human family. But the Baalim were as multitudinous as their worshippers and the high-places whereon they were adored; there was little difficulty, therefore, in identifying the gods and "spirits" of Sumer with the local Baals of the Semitic creed.

El-lil became Bel of Nippur, Asari or Merodach Bel of Babylon. But in taking a Semitic form, the Sumerian divinities did not lose their old attributes. Bel of Nippur remained the lord of the ghost-world, Bel-Merodach the god who "raises the dead to life" and "does good to man." Moreover, in one important point the Semite borrowed from the Sumerian. The goddess Istar retained her independent position among the crowd of colourless female deities. Originally the "spirit" of the evening-star, she had become a goddess, and in the Sumerian world the goddess was the equal of the god. It is a proof of the influence of the Sumerian element in the Babylonian population, that this conception of the goddess was never forgotten in Babylonia; it was only when Babylonian culture was handed on to the Semitic nations of the west that Istar became either the male Atthar of southern Arabia and Moab, or the emasculated Ashtoreth of Canaan.

The official religion of Babylonia was thus the Baal-worship of the Semites engrafted on the animism of the Sumerians. It was further modified by the introduction of star-worship. How far this went back to a belief in the "spirits" of the stars, or whether it had a Semitic origin, we do not know; but it is significant that the cuneiform character which denotes "a god" is a picture of a star, and that the Babylonians were from the first a nation of star-gazers. In the astro-theology of a later date the gods of the pantheon were identified with the chief stars of the firmament, but the system was purely artificial, and must have been the invention of the priests.

The religion and deities of Babylonia were adopted by the Assyrians. But in Assyria they were always somewhat of an exotic, and even the learned class invoked Assur rather than the other gods. Assur was the personification of the old capital of the country and of the nation itself, and though the scribes found an etymology for the name in that of An-sar, the primæval god of Sumerian cosmogony, the fact was always remembered. Assur was purely Semitic in his attributes, and, like Yahveh of Israel or Chemosh of Moab, was wifeless and childless. It is true that a learned scribe now and then found a wife for him among the numerous divinities of the Babylonian cult, but the discovery was never accepted, and Assur for the mass of his worshippers remained single and alone. It was through trust in him that the Assyrian kings believed their victories were gained, and it was to punish those who disbelieved in him that their campaigns were undertaken.

In the worship of Assur, accordingly, a tendency to monotheism reveals itself. The tendency was even more pronounced in a certain literary school of thought in Babylonia. We have texts which resolve the deities of the popular faith into forms of one god; sometimes this is Anu of Erech, sometimes it is Merodach of Babylon.

Babylonian worship necessitated a large hierarchy of priests. At the head was the high-priest, who in early times possessed temporal power and in many states was the predecessor of the king. The king, in fact, inherited his priesthood from him, and was consequently qualified to perform priestly functions. Under the high-priest there were numerous classes of ministers of the gods, such as the "anointers," whose duty it was to anoint the holy images with oil, the ordinary "priests," the "seers," and the "prophets." The prophets enjoyed high consideration; they even accompanied the army to the field, and decided whether the campaign would result in victory or defeat. Quite apart from all these were the astrologers, who did not belong to the priesthood at all. On the contrary, they professed to be men of science, and the predictions of the future which they read in the stars were founded on the records and observations of former generations.