I was playing through Morrowind again, and was looking at it from a tactical point of view, and realized that the Empire would have had a hard time of conquering Morrowind except for the Ascadian Isles region (which is relatively flat terrain, perfect for a phalanx). But getting toward the Molag Mar region and the Balmorra regions, it becomes hilly and heading north from those points it goes from hilly to mountainous. And heavy infantry (like most of the famous ancient civilizations had, like the Greeks, Romans, and Babylonians) perform poorly in those situations, especially if confronted by light infantry, which the Ashlanders fight as.
Also, what kind of calvary does the Empire use? Heavy (like knights) or light (basically mounted archers, like the Huns used). Or do they use Chariots?
I don't see why the Imperials would use the Phalanx formation at all, the Imperials Legions are allmost exact copies of the Roman Legions(at least the eastern ones)and if anything, would be using formations such as the tsudo formation.
But as with any invading army, they will not waste time sprawling thru the rocks and hills and wastlands when they first come, they will only capture areas of tactical importance, and would only attempt to capture the less desireable parts of the land(if they would even bother at all) when those areas are very well secured.