i have to disagree with the previous reply about the time, keep an eye on it. it stoped me sometimes cuz i was out dinking around. so this is how i did it.
for starters make a wall of protection at the base with your troops. you'll be attacked from almost every side.
build a turret building then put up you actual turrets, i had about 3 or 4 anti-V and at least 2 anti-A. while your doing this send for some more troops some artillery and some at st for sure your gonna need some moble anti air too, so start to build up about 4 to 5 of those over time. take a squad of a hand full of troops (6) in a troop carrier (i had about 3 of them) some atst an anti air (just in case) and raid the control stations (which are on the bottom of the map when you looking at it in the map in theBHCI) once you have those leave a trooper inside them and go back to base. during this time build an landing base and get some ties
your gonna go to the drill now. your gonna need alot of firepower. on the back side of the drill is an air speeder base and each one of the turrets, send a good sized attack on it. i recommend 5 atst, acouple anti air and about 3 to 4 artillary. they do the damage on this level. take out the air strip for sure and try to hit the anti air. once that is done you take then back up to the drill. while you were attacking the airstrip, send the rest up the first side of the volcano. have artillery to do some troop attacks, send in ties to keep um busy. once the lower base is taken out storm and i mean storm the upper levels of the drill area, your time should be cutting down. remember those troop carriers i said to get, well have one loaded with Dellis and 5 storms close but not in harms way. send the other troops carriers (1 or 2) up to the drill and clear it out. once thats cleared out send in Dellis, or you could send him in with the troops, i did that and he didn't take to much damage, but put the smack down himself.
MAKE SURE YOU HAVE THE TIME TO DO THIS, I HAD TO DO THE LEVEL OVER CUZ WHEN I SAVED LAST, AND WITH THE TRIP UP THE DRILL SITE DELLIS COULD HARDLY GET IN AND TIME WOULD BE UP. once you have control of the drill, time stops and never restarts, you have to take out the rest of the rebels, make sure all air units in the rebels power are delt with. order atst's and artillery send them down the volcano over to the rebels wipe them out, all of them. i did recon with the ties, quick flights over the un explored areas, in ever case i had the numbers to kill so. this level is all about numbers.
the drill is first and formost objective.
like i said the artillery is the best, be aware that they have to have a spotter, another unit, any unit, to be around to spot and the art does the rest.
"I will not tolerate failure!"