From the Steam store page:
Command or corrupt an entire galaxy in the definitive Star Wars strategy collection. It is a time of galactic civil war. Will you take up the reins of the Rebellion, assume control of the Empire, or rule the Star Wars Underworld?
Star Wars Empire at War:
From the lives of soldiers to the deaths of planets, you are the supreme galactic commander. It is a time of galactic civil war. Take up the reins of the Rebellion or assume control for the Empire. Whichever you choose, it will be up to YOU to steer your side to ultimate victory. Command everything from individual troops to starships and even the mighty Death Star as you execute campaigns on the ground, in space and across the galaxy. Forget tedious resource gathering – just jump straight into the heart of the action. You can even change Star Wars history! Every decision affects your next battle and every battle helps shape the fate of the galaxy.