Can you help me find this game? I can't remember its name!  

It was a PC game, I used to be addicted to it, I played it a few years ago, but I really can't remember it's name!
I can tell you everything I remember about it, every little detail, except for the names of different things, I'm terrible with remembering names! :(

It was a game about soldiers. The goal was to build some academies or something similar that would create more and more soldiers. That troop could scout the surroundings and attack the other enemies, until they cleared the whole area.
There were also some blue crystals from which some kind of small blue robots extracted energy which was necessary for building those structures.
Some of the enemies were aliens and strange creatures and the game had several levels.
The characters in the game were all very small, like in "the cultures" game, heroes of might and magic or other games with vikings.

Do you have any idea which game I'm talking about? I'd appreciate any help!