The Assyrian Empire is documented in, among other works, Herodotus's Histories and Book II of Diodorus Siculus's Bibliotheca Historica, two of the most influent

The Assyrian Empire is documented in, among other works, Herodotus's Histories and Book II of Diodorus Siculus's Bibliotheca Historica, two of the most influential histories written in classical antiquity. To dismiss the these sources as merely "some Greek manuscripts" is misleading. Also, at that point, any pre-19th century debate about the historicity of the Assyrian empire is no longer just a quarrel with the Hebrew Bible, but a wider skepticism of numerous ancient and independent sources. I don't think you can provide an ancient Greek source that is skeptical about the existence of the Assyrian empire. There's a quote from Lucian's satirical dialog Charon that people try to use to for that, but I don't think it works. In the dialog, Hermes notes there's no trace of Nineveh left, suggesting Babylon would soon share the same fate. Never mind that at the time Lucian wrote that (2nd century AD), Nineveh was still standing and inhabited. Nowhere does Hermes suggest Nineveh never existed. As for Sennacherib's Annals, the similarities are: * Jerusalem was under siege but was never taken. * Hezekiah paid tribute to Sennacherib. * Sennacherib returned to Nineveh after the siege instead of continuing his campaign. The differences: * The Hebrew Bible has the Assyrian army being defeated by an "angel of Yahweh" killing 185,000 soldiers in an unqualified defeat. The Annals have Hezekiah abandoned by his mercenary and allied armies. Then, Hezekiah is overwhelmed by Assyrian power and pays the tribute to end things. He submits as a vassal. * The Bible has Sennacherib treacherously continue his attack after being given tribute. The Annals have the Tribute ending the siege. * The tribute the Annals record is much larger than in the Bible, including 200,150 people, uncountable livestock, in addition to the aforementioned gold and more than double the silver mentioned in the Bible. Both accounts are royal propaganda and need to be taken with a grain of salt. It's hard to say what really happened outside of where they agree. Outside of the conflicting accounts, the siege of Jerusalem comes around the time that Babylon again went into rebellion. That seems to explain the end of Sennacherib's campaign better than an overwhelming defeat by a minor vassal king.