My basic formula for raiding via ground was like what he said. Midrange missiles combined w offensive antiair. Target any structure like the capital, state corps, city or fort, and hit the defenses first before the actual target. This will eliminate any garrisoned weapons in that structure and the anti air will take out some of the copters, your main threat. Once the garrison defenses are done on one structure repeeat the same defenses attack on another intill all copters are kaput. Then have fun using your mid range missiles and destroy the now helpless forts, corps and cities. And keep painting the map! Good damage points there. That basically means just keep your units moving on the battle field occupying land. If this were a pvp (player against player) the strategy alters and that's a whole other discussion.