Just finished playing this game, again. I won of course, got through all the levels with only a few hiccups along the way. The best way to beat this game is to 1. protect your base then 2. send out scouting parties to find more resources then 3. send a small patrol to guard those resources and the path your mining crew follows to get to them then 4. send out large patrols to kill the enemy
If you try to do it any other way chances are you wont live long. Either the enemy will overpower your base, or destroy your mining crew and get to the resources before you do.