i'm also forget, capture until you have 3 planets under your control and develop it with Power Plant and Mines first, so if your planet ever get captured, it will be easier to take back.
You know? The reason you cannot win the game is that you rather play safe than take a risk of losing more troops. This game is actually quite challenging though, but if you get your strategy right, it will be easier to defeat all campaign and skirmish. I recommend build 20 Fighter on early battle and always build Power Plant and Mines first before anything, until it enough to actually build anything.
 "Strike Force Heroes 2"){kind=icon}
 "Star Squadrons"){kind=icon}