Just a discussion here.
Which force in Tamriel can conquer it ?
When I say Argonian Empire, the Argonians get the Hist mind control.
Aldmeri Dominion ( at its full potential )
The Empire ( at its full potential )

None of the above should be an option.
I vote an army of Draugr and dragons.

But they can't gather enough numbers.

Dragons and the undead of the Dragon cult

There are a lot of Undead in Skyrim, and many of them have the Voice

All that is keeping Mundus safe is lonely Valdar, ever vigilant in Valthume. I give the next best chance to the Argonians, the Hist makes them formidable.

Nords as a unified Military Force have proven thier abilities time and again. The Bosmer Wild Hunt getting lucky is the only reason Nords did not conquer all of Mainland Tamriel in the First Era.

Aldmeri Dominion is the only one who has enough power and interest to conquer whole Tamriel. But now it seems there are many strong powers on Tamriel and so conquering it won't be easy.

Empire.

The Dominion is too weak and hated, indies are too weak individually and Argonians... well, they couldn't even take over Morrowind in its darkest hour so I wouldn't expect them to get far anywhere else. Besides, most of Tamriel would never accept being ruled by beasts.

The Empire was the strongest with the Nords, Bretons and Redguards behind them but the Thalmor have cleverly engineered schemes to weaken their alliance. The Imperial are still powerful but due to the civil war they now lack the war-hardy Nordic infantry and smiths that Tiber Septim had behind him. Plus any support of units like shrewd desert raiders and bowmen of the Alik'r or the mighty mages of High Rock.

I think in Skyrim we have had a teaser that the Aldmeri are searching magical artifacts which will give them a much greater power. Plus they are seeking the technology to build better armor (Skaal). I think we may well find that they will be able to take Tamriel (except maybe Black Marsh & Morrowind for the time being) but I have little faith in them to keep it. Unlike the Imperials the Thalmor rule with oppression and racist views. At least the Imperials are good at diplomacy.

For the Argonians to take anything then they at least need the Dunmer backing them which has little chance at present. Argonians may be ferocious on their home turf due to inhospitable terrain that others would not know how to deal with but on foriegn ground they have little strength other than assassins and rogue which on a open battlefield offers little. When they sacked Morrowind it was a time when the Dunmer were weak and not suspecting it. Unless the Argonians are still in power (which could be the case as we are yet to find out) it would apear that the Argonians soon made way back to the terrain that keeps them safe from outsiders. If the Argonians are however still in power then we have signs of Dunmer moving back and considering it safe which means the Argonians be integrating better with the Dunmer and may even have them within their ranks. As for the Hist then i think it maybe massively over-rated. Especially once outside of Black Marsh. The Argonians on the docks of Windhelm and the streets of Riften are hardly a force to steer clear of.

The only 'force' that will be able to take Tamriel is the Ginyu Force.

I think an army of Hist-pumped Argonians could take over Tamriel. But they wouldn't, the Argonians have always been isolationist and I don't see that changing any time soon.

The Armies of Mordor!

Failing that the Argonians stand a good chance.

GLORY TO THE PEOPLES DEMOCRATIC REPUBLIC OF MUDCRAB! HAIL CHAIRMAN MUDCRAB!

We don't know the motivation of the Hist in that invasion, we can only guess and all we have is one-sided views. We can't evaluate how much is it because the Argonians "failed" to conquer the North despite that being the master plan, or is it just the invasion was technically over from the Hist perspective once they got their lands back (southern Morrowind which was rightfully part of Argonia). The Dunmer fans like to emphasize that an army of Redorans pushed back the whole "Argonian invasion", but we don't know exactly if that was the full force Argonian invasion under Hist control, or just loose skirmish parties and raiders acting individually, once the hivemind was over. Argonians are not conquerors by culture that's for sure, but that doesn't necessarily mean they can't be strong invaders and keep the occupation when that's the Hist will. In the case of Morrowind they could simply have no intention to annex the province, except the south lands that were theirs and more hospitable for Argonians. I think, given the radical An-Xileel faction being now the harsh rulers of Argonia, there's a good chance they will become an increasingly aggressive force towards other provinces.

The Argonians on the docks of Windhelm are not warriors or invaders, they're a bunch of poor commoners. Had they been "prepared" by the Hist for war, they'd surely be a force to steer clear of. Ask the Daedra

what about the SAS (Skeever assault squad)

Argonian Empire would have the best chance. Just look at what they did to the Daedra during the Oblivion Crises. Second best chance would be the Cyrodiilic Empire.

argonians? you mean the people that couldn't even take morrowmind when it was in such a weakened state? yeah, no

The aldmeri dominion vs the empire, while both sides were devastated, the elves came out in a better position, so them

Chumps, the lot of them.

At the time of Skyrim, 4E201, I don't think any force can conquer Tamriel. Just about every faction available is either too weakened to do it, even if they once were able, or they were never strong enough to do it to begin with. And the only one who managed to fully conquer Tamriel was Tiber Septim, with the help of a huge dwemeri robot that breaks time. Without such a powerful artifact, I think conquering Tamriel is a task beyond any faction.

The Reman Empire, with pretty much all of Tamriel behind him, short of Alinor as far as I know, warred with Morrowind for 80 years before he achieved a truce that gave their Empire less influence in that province than Tiber Septim's truce with them. And the Reman Empire had help of the Akavir, who had carved right through Morrowind and long into Skyrim and Cyrodiil before being stopped(partially due to a natural disaster in their head quarters from what I gather). And he didn't have to conquer High Rock or Skyrim, making the start of his Empire much easier.

The kingdom that was to become the Septim Empire was in danger of being eliminated early on, when the Nords and Bretons sent an army to stop this warlord before he could become a threat to their nation. Hadn't Tiber been able to make the risk he took pay off, his army would have been destroyed against the superior Nordic and Breton forces, who were better supplied, prepared for a winter campaign and arguably more numerous, being from Skyrim and High Rock instead of a single Colovian kingdom. But it payed off and his army swelled up with well-trained, well supplied veteran Nordic troops and generals(and this led to joining Tiber's army being common for young Nords for ten years before Skyrim even joined his side) that allowed him to unite Cyrodiil and officially start the Septim Empire. And he won Hammerfell through uniting with the losing side of their on civil war.

The only province he won without already having a foothold in it and among it's people, or without the help of a giant mecha, seems to be High Rock. And it seems he never had all that much control over that nation, because of all the warring smaller kingdoms. At least the 9 Jarls of Skyrim would be easier to keep track off than around 50 kingdoms.

Edit: I think that an Argonian Empire wouldn't have much chance. They can defend their home from just about anything, but beyond the borders of Black Marsh they seem to be limited in the capacity to take over. And the further away from Balck Marsh, the weaker the Hist's influence becomes, limiting their trumphcard quite a bit.

For the Empire!

Yeah, that's what I think about the Hists, they could create endless invading forces but they don't need to. All they care about is Black Marsh and its safety. Anyways the Hists as described in the lore especially in the novels are a formidable powerful being since they can create Argonian life form and shape it to suit particular roles. That, combined with the well known Argonian resilience (physical and mental), guerilla war skills and their selfless kamikaze behavior, they're probably the most powerful potential force of the whole Tamriel.

The Argonians shall rise and take Tamriel.

The Empire.

Larger base of support, more land, more men, more resources. The Dominion is strong but i doubt it can rival the Empire when it's at full power.

in their current state, they couldnt take all of Tamriel.

"The Empire ( at its full potential )"

At it's full power the Dominion would be nothing but a speed bump.

Not at the moment, no, but assuming that Skyrim remains a part of the Empire one way or another and the Empire defeats the Dominion (which they will), they will stand as the strongest entity in Tamriel and it's just a matter of time for them to purge the rest of the continent.