Got the game, fairly impressed.
Take an RTS like Command & Conquer: Generals.. now.. require research and A LOT more buildings to be constructed. You now have Rise of Nations.
It took me a couple of tries to get used to the gameplay/requirements from various buildings. Then I finally figured out that every city you build, to expand your empire of course, requires five essential buildings. Once those are built, and you span the ages through further research you begin to add more to those cities. Suddenly you are given "wonders" that add more capabilities to your empire. One wonder per city, which requires you to stay fairly equal with your opponent or risk a "wonder victory" for either side.
Now the military! As you span the ages, your units are upgraded automatically AND you can research a better unit to further upgrade them, unless you are at the Information Age (our present age). The game automatically groups them into battle formations for easier deployment. Every unit has a weakness and a strength, so using them wisely helps. Just as in Generals you can build forts, anti-aircraft weapons, ect. However, this game allows you to build generals, spies, and scouts. All of which can do useful "behind the scenes" actions. Aircraft, once you hit the industrial age, are similar to General's design EXCEPT you can actually call all aircraft from one base back from a mission from thier home base.
From the map I was playing.. it only took me an hour to finally beat my opponent, this was on easy though. Multiplayer would be interesting, though I fear with research playing a major role in the game there would be balancing issues. Balancing being that you could suddenly be invaded by someone in the Gunpowder Age and your still fucking around in the Classical Age. To get an idea of how badly that could go.. imagine one side throwing spears while the other simply aims rifles and fires.