> In your opinion, what is a good argument for territory?

If I had one, I would be a moderately successful philosopher instead of a moderately successful software engineer :-)

I don't think there's a good "just" definition for control of territory: claims of original or ancestral ownership are hard to verify (and subject to this kind of hell-in-a-cell irredentism), while "working" definitions uniformly favor the most ruthless or powerful party.

Instead of arguing for rightful possession on lines of originality or power, I often think counterfactually: who would, all things being equal, be the ideal stewards of a piece of land? Under that framing the answer is almost always a secular, liberal democracy where national ties are more significant than ethnic or religious ones.

Very few of those exist, and the ones that do are strikingly imperfect.

> A question I have there is how far back to do you have to go to reach that ancestry.

It really depends on what you mean by "reach." As noted above, the Ashkenazim had a significant population bottleneck event, and are genetically distinguishable from other peoples living in Central and Northern Europe. Whether that makes them "closer" to Levantine ancestry or not depends on your perspective: you could argue that they admixed relatively little given their isolation from their original ethnic group, or you could argue that the admixture that occurred was proportionately significant.

> Correct me if I'm making a logical error here, but this would suggest that Ashkenazis likely originate from a voluntary diaspora and not a involuntary diaspora (like in 70 AD), if they share genetic ancestry to the region from around or just before the Kingdom of Israel and Judah were established (unless they were expelled by their own. i.e. the equivalent of different denominations and ideological schisms).

I don't know if it's a logical error or not, but it's an incomplete picture:

* The Jews that became Ashkenazim left the Levant in multiple waves, for multiple reasons (anthropologists will say things like "push and pull factors," which really just means "some were pushed out by hardships, and others were pulled away by opportunities, etc.").

* The likely ancestry of Ashkenazim dates back to ~900-1000BC, but this doesn't itself represent a date range for when they left the Levant. To make it intuitive: there's no distinction between someone living in the Levant in 300 BC with that ancestry and someone living outside the Levant with that same ancestry: they'd look the same in terms of the genetic record.

* Historical records aren't very detailed for the period, but a significant record of Jewish Levant-Europe migration comes from the decades following the Bar Kokhba revolt. Josephus (who is Jewish, but is writing as a Roman citizen) records around 100,000 enslaved on just one occasion among several[1]. These slaves were likely transported further into the empire for labor in both Greece and Italy, which in turn is a likely explanation for the Southern European genetic component within the Ashkenazim.

TL;DR: There's more than one factor that explains the flight of Jews from the Levant. However, our strongest historical record for large scale migration strongly suggests that the bulk of what became the Ashenazim arrived in Southern Europe in the first and second centuries, and then moved further into Central and Northern Europe during the Late Empire and Early Medieval periods. That migration was in turn primarily caused by "push" factors (mass enslavement and murder following the failure of the Bar Kokhba revolt), followed by subsequent "pull" factors (subsequent normalization of Jewish status in the Roman empire, stable lives outside of a post-temple Levant, etc.).

[1]: https://www.gutenberg.org/files/2850/2850-h/2850-h.htm#link6...