As long as you are producing a constant stream of Star Destroyers the Rebels and Black Sun shouldn't be a problem, they can hold as much ground as they want, but the Empire has the ultimate ground removal card in the Death Star once you save up the credits. You're going to lose infantry but in the Empire that's what I think they call acceptable casualties.

(Which also if you're being harrassed on planets by rebels and black sun infiltration units, put down an artillery piece with two stormtrooper units, you'll never have a problem with raids again) Artillery isnt good at much more than wiping out infantry but it helps clear the field so you can focus on vehicles.

(mercenary recruiters are actually pretty useful, they let you purchase a unit while in battle)Д¤ Deploy the garrison aka drop 3-4 more units of stormtroopers mixed with anti-armor troops, along with a unit or two at AT-STs, an imperial artillery unit and any remaining spots for my AT-ATs and Veers or if I'm feeling ballsy a hero unit like Vader/PalpatineДҐ Advance with my AT-AT blizzard force on point with infantry directly behind to rush in at a moments notice, AT-STs behind them and artillery bringing up the rear always within firing range should the enemy rush. I've pretty much conquered the galaxy at this point with the empire, which from what I've read is the easiest faction to win as, my strategy for ground combat was exactly what I think yhe true empire would do.ДЈ Scout area with ties, locate any weak spots or buildings of interest power generators, turrets, mines etc.

Awakening of the rebellion manual