One of the best RTS games ever made.
It is a mix between an action shooter and an RTS. You pilot a tank of some sort the whole time (unless it gets destroyed, then you are on foot till you acquire a new vehicle), and actually get to participate in the battles.
Takes place during the 60s-early 70s of the Cold War. US and Soviet Union are battling it out for control of a new metal they call, Bio-Metal 11, or just bio-metal. US has creaded the NSDF (National Space Defense Force), and the Union has the CCA (Cosmo Communist Army). You play on the Moon, Mars, Venus, Io, Europa, Titan, and eventually, a fictional moon orbiting Uranus (no jokes) called Achilles.
And there is a twist in the story, but I won't give that away...