bucked convention when they released Shogun: Total War
. Shogun combined turn-based gameplay, which was at the time all-but-dead, with real-time strategy. Rather than the standard "gather resources, build, harass, and attack" RTS gameplay, Shogun had the player fight battles with the units he brought over from the turn-based portion of the game.
Moreover, those battles used realistic units and tactics. Every individual was rendered, modeled, had its own AI and statistics, and would work as part of a unit. Of course, they had to be deployed properly, so rushing your cavalry against spearmen wasn't almost as bad an idea as leaving archers too far out in the open. The game engine supported advanced concepts like the advantage of higher terrain, the importance of having deep lines to resist charges, and the effect of weather on archers and gunners.
As soon as Shogun was released, development started on Medieval: Total War
and Rome: Total War. Medieval, using the Shogun engine, was released 18 months ago to considerable commercial success thanks to its improved gameplay (if poor interface.) Development on Rome continued in the meanwhile up until the present day.
Screenshots and feature lists were released a long time ago already, and it's hard to believe that the game has made the transition from 2D sprites on a 3D map to being fully 3D, but it has. Even the strategic map is 3D. In fact, the terrain that your armies traverse on the world map is what gets translated into the battle map. If your army was following a road with mountains on the North and a plain to the South, then that's what your battle map will display.
The maps have also gotten a great deal larger. I don't believe the exhibitors from Creative Assembly explained how much larger, but the difference was quite visible in the multiplayer scenarios we played. In a rough estimate, I'd guess that the total area would be at least four times greater, meaning that a map would be twice as long and twice as wide as it was in Medieval. This extra maneuvering room factors into the gameplay a great deal, it allows players to sneak behind hills or through forests, and makes a world of difference in team-based multiplayer, such as we played at the event.