So just now I got my russian base blown to bits after one of the larger alien ships, a cruiser most likely got through the plasma turret and landed troops. I only had 5 rookies, one got mind controlled so I machinegunned him down with another guy, my assualt was able to shotgun down one alien, then suddenly tons of aliens came from the barracks room which I had no idea would contain aliens and killed everyone. How should I defend bases on the ground?