yes but they couldn't hold it, so the map of Hammerfell would look the same

That seems accurate. Thanks for posting. Been looking for something like this

Oh, my mistake. I was under the impression that they were still there fighting over territory. Guess I missed the details.

Until very recently, they were (4E 190-ish iirc)

I thought the Argonions only attacked because the Hist told them to, and after the invasion they mostly shrank back into their swamps.

http://www.imperial-library.info/content/rising-threat (this book should get included in the Lore FAQ as required reading) explicitly hints that the Thalmor manipulated the Argonians into attacking Morrowind. Whether the Hist told them to or not is open to debate (I fall on the not side), just like whether the Thalmor actually did manipulate them, but yes they pretty much only seized up to about Tear at our last estimate.

I think the way it goes is that the Thalmor more or less suggested to the An-Xileel that an invasion would be opportune, but unfortunately for the Thalmor, the Hist were already making plans to do that. I don't think the Argonians were ever under Thalmor control or significantly influenced by them. That's my assumption, at least. I doubt entities like the Hist would be bossed around by a bunch of Mer like that.

I'd say the author of Rising Threat is biased and attributed every possible thing to the Thalmor. The Hist didn't need to be manipulated to see the attack as a good thing (and I doubt they could be manipulated by an elf). I even doubt the Thalmor sent agents to Argonia... And how would they get any influence there?

Do Hist=Blackmarsh though?

If by Black Marsh we mean Argonians, than mostly yes. And definately yes if we are speaking on the scale of preparing an invasion on a different province.

What I'm asking is that do the Hist have a complete 1:1 control of the Argonians? After all, Blackmarsh has (had?) a king who in the past needed a band of personal assassins. If he was just a pawn of the Hist, then why did he need to preserve his power? Who does he need to fear from? Other Argonians? Surely the Hist wouldn't let that happen.