First of all yu make ur base denn with the stronghold clik on it and make loads of space marine squads denn put a square aroung all of them and go to a little purple ghosty/alienish head in da corner and it will say infiltrate and all ur men will be invisible to the enemy so denn yu can upgrade your guns and go attack that enemy

.:warning:. yu have to take off the invisibility/infiltration so that they can attack but it wont matter bcuz the enemy will be so shocked with men just appearing that you will defeat them