The Assyrians were the probably the first major power in the Levant that practiced pacification through hegonomy, i.e., the imposition of standards of government, taxation, political affiliation and, most importantly, religion. The indigenous peoples were required to reform their worship along the lines of the Assyrian chief deities, although the locals were allowed to call them by whatever name they wished.
The Assyrian vassal treaty that forms the core of Deuteronomy was indeed a reform imposed from without. The cherubim iconography of the writings and of Northern Israel temples stems from this period, but Hezekiah and others were not cleansing the religious system of idolatry, but instituting the “correct” form, under the directives from their Assyrian overlords. The Assyrian highest god, Asshur, became the first model of what was later to morph into YHWH.
Other native city states, such as Judah, were also introduced to the new concept of Henotheism, the belief that although there were many gods, there was only one chief God. The northern kingdom of Israel was eventually overrun by the Assyrians, who imported in non-native peoples who quickly mixed with the Canaanites, the records of the statelet being transfered to the notoriously literature-hungry Assyrians. Later the city-state of Judah, centered in a newly prosperous Jerusalem, was also absorbed into the Babylonian empire, heir to the Assyrian records, among other things.
The Henotheistic exiles were purposefully isolating themselves into a distinct group while in captivity, who found that it was theologically impossible to worship their chief god, a form of Baal-Asshur, called YHWH, in a land that was under control of another god, Marduk. Zoroastrian religion was filtering into the Babylonian empire and the exiles converted to a form of it, a system near enough to be considered Zoroastrian, but having the monotheistic-trending god, YHWH, as the name of the God of Heaven, thus necessitating to account for “Mazda,” as explained below. As Zarathustranism turned to polytheism under the influence of Babylon, the exiles became ultra-monotheistic, rejecting all other gods, which represented everything bad that hitherto had happened to them.
The book of Daniel is actually a tale of the subversion of Babylon by a disloyal internal force, the ancestors of the people resettled into Judah. Daniel interprets the writing on the wall, declaring that the "Most High God" has decreed an end to the empire of the Chaldeans, and "In that night was Belshazzar, the king of the Chaldeans slain. And Darius the Median took the kingdom...." [KJV, Dn 5:30, 31]. By this time, the now ancient Daniel is decked out as "third ruler in the kingdom," a convenient position from which to influence subsequent events.
Cyrus, king of Persia, favored the Juddin of Babylon, as they were called, at first, but eventually found it expedient to encourage them to govern hostile territory in Judah, establishing a temple and tax-collection statelet for "all Jewry." Here I interpret Jewry, another variant of Juddin, as a non-ethnic, religious distinction. When they arrived, their religion and holy writings fasioned in the libraries of a Mesopotamian land, encountered native Canaanites heavily influenced by Egyptian culture, as the Levant had been mostly under their control before the Assyrians. The tensions between Persia and Egypt were mythologized into Egypt vs. the Israelites, or vs. God himself.
These Canaanites that lived in the land of re-settlement were still worshippers of YHWH and El, but were now seen as unclean and outcast pagans, as devotees of demons, and as forgetters and perverters of the “true worship,” a mythical system synthesized during the Babylonian captivity and fasioned after worship of YHWH (Ahuramazda) as the God of Heaven. The reluctance of the Juddin to voluntarily settle in a “land of promise” and the resistance of local worshipers of El, various Baals, including YHWH, led a forced settlement under Darius II, later mythologized as the forced migration of slaves in Egypt to the land of Canaan. Persian loyalties made it literarily inevitable that the main antagonist of the Hebrew writings be burdened upon the Egyptians. Nevertheless, the indigenous population of Judah contributed much to the ever-evolving collection of writings that provided the statelet with its national mythology. The pre-exilic kingdoms of Israel and Judah were myths, likewise based on the surviving records of the various conquerors, a Jewish southern kingdom having been woven out of parallel events recorded of the actual historical northern kingdom.
As Mazda mutated into Moses at the hands of Alexandrian Juddin, spurred by antagonism between the Egyptians and Persian-loyal Juddin, or Jews, living there, a Hebrew work was created to weld together the exilic and post-exilic story of the Jews, presenting the Egyptians as the main enemy. Just as Persia had detested all things Egyptian, their Juddin descendants, once Persia was neutralized by the Greeks, continued to see the Egyptians as their chief antagonists. As knowledge of Hebrew died out (Aramaic had already displaced it by this time) Greek translations became necessary. Since Hebrew was probably a dead language by this time, to write extended literary works in this language should be interpreted as an effort at deliberate archaizing.These Alexandrian romances were, over an extended period, translated into Greek and redacted, becoming the Septuagint, an ongoing work probably until the time of Herod the Great.
The myth of the Septuagint, as recorded by some ancient writers, can be seen in many ways as a deliberate inversion of the actual circumstances. The Hebrew texts were not imported into Egypt, but were in actuality created there, and allowed to become moth-eaten and corrupted by copyists. Later the Palestinian Jews imported what remained of the older texts, supplementing the many corruptions by “reverse-engineering” the Septuagint into Hebrew where necessary, making editorial changes, etc., a process that possibly continued at Qumram.