Its not up to the Argonians.
I made a pretty good case in that thread I linked.
Yes, that was a great assessment Merari.
I wrote this to explain the Ebonheart alliance:
Its not impossible.
If the threat is Cyrodiil then it makes geographic sense for one.
The living gods of Morrowind are at full power, or very nearly that, and possibly the neighbouring provinces seek protection from them in the form of an alliance.
I can see Vivec or Almalexia agreeing to that, if they got something in return.
Hlaalu wouldnt mind favourable trade agreements, Dres could get slaves out of it.
Indoril would follow the Triune, Redoran wouldnt care one way or the other and be insular, and Telvanni would be firmly fragmented with an official stance taken by Telvannis but each mage-lord just doing what he himself wants anyway.
In fact, if the Dunmer milk their position as most powerful and umbrella member of this alliance for all they can get, it goes some way to explaining later hostility between the Dunmer and the other two.
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On the Argonians, the most important factor is the Hist, who by their very nature we cannot understand.
Their machinations are long-term and alien.
It is quite possible that they would hand over territory and Argonian slaves, for all we know an individual Argonian is not that important to the Hist, who have a hivemind themselves, in exchange for protection against a threat.
It is not beyond the realm of possibilities that the Hist already know enough about future events, or are capable of such longterm and intricate machinations that they see this as a temporary setback.
They might already know they get everything back and then some after the events of the Red Year, post Oblivion crisis.
What the Argonians themselves think is I believe largely irrelevant.
Note the Oblivion rumour where many Argonians heeded 'the calling' and returned to Black Marsh.
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The Nord and Dunmer have worked together before, for instance against Dwemereth, and will do so again, for instance after the fall of Baar Dau.