The apocryphal book of Judith opens with geopolitical circumstances which I cannot locate in history. Assyria is lead from Nineveh by a king Nebuchadnezzar and conquers Media, most of Mesopotamia, Tyre and Sidon, and parts of Palestine. For those of us familiar with the ancient near east and biblical history, Nebuchadnezzar was the Babylonian king who threw off Assyrian domination and destroyed Nineveh.
In the fifth chapter things get more confusing. Nebuchadnezzar’s general inquires of the history of the Jewish people, and an Ammonite recites the story of Israel. The history he recounts goes from Abraham clear through the return from the Babylonian exile. That return of course occurred after the time of Assyrian power and Nebuchadnezzar’s reign.
So the setting of Judith seems ahistorical. I am by no means an expert on ancient near east history, so I could be wrong. If there is an alternative explanation (e.g. this is simply a case of mistaken identity and Assyria was indeed powerful during the intertestamental period), please comment or email me. Until then, I’ll look for significance in this book outside of its depiction of geopolitics and history.