awesome, fire emblem through to advanced wars with a little anno thrown in.
i like the look.
Well, the PC versions were an empire building type of game.
You started with a group of settlers and one or two warrior type units. You used the settlers to establish a city, which then could build city buildings, settlers(can also make roads and things), and warrior type units. New settler units could be moved to create more cities, build roads(faster movement, also rail later), improve terrain, etc.
Each city dependent upon where it was built would provide a certain number of resources, gold, food, etc.
There was also a research component in which you got X number of research points per turn, pick a technology from a technology tree, and after hitting the number of points for that tech, you got it which could unlock other city buildings, warrior units, improvements, gold production increase, knowledge production increase etc.
There were also trader units so that you could set up trade between your cities and and other player's cities.
Additionally, there were also the wonder improvements that you could build that would give various improvements.
The goal was varied, either conquering the entire world, having the most "points" at the end of X turns, largest empire, etc.
Not sure what or how it will be implemented for the DS though.
A not very correct version of warrior type improvements would go:
warrior -> phalanx -> man at arms -> musketeer -> infantry -> mechanized infantry
scout -> cavalry -> knight -> dragoon -> tank
There were more units in there and they did not ALL depend upon prior units, but I really don't recall the exact progression but that should give you an idea.
I should also mention that units included water units as well ranging from fishing ships, trading vessels, to battleships and aircraft carriers IIRC.
In later stages of the game there are also aircraft units.
There should be a wikipedia entry for this game series if you really want more/better descriptions of the game.