User blog comment:StarkBlack/Most Powerful Province?/@comment-10207438-20131018002614

people who say Cyrodiil are not taking into account that Cyrodiil isn't using a 'Cyrodiilic army' they use the Imperial Legion, which is a force that pulls in people from all other provinces, without the empire they have no standing army, this makes them weak, and the fact that they're surrounded by other countries makes invasion much more likely, and as can be seen in... well pretty much all of tamrielic history, Cyrodiil is easily conquerable.

My money is on High Rock, Summerset, or Blackmarsh.

However, if out of nowhere all countries just up and waged war against everyone, I'd say Blackmarsh wins hands down, hell the only country that might survive against a war with the argonians would be highrock, and only because it's the furthest one from blackmarsh.