this may take some time but i beat the mission with a decient amount of people left. first go down to the command center with 4 or 6 troopers and capture it. luke is inside he pops out and is usable by you. ok now this is the long part use luke's secondary ability and scan the entire screen.
use a non permanate marker and mark on the map where all the yellow allies and the blue turrets and enemy locations. take over the 2 turrets buy the mobile command center once that is done. take 4 or 5 troopers to the artilery unit by the command center but wait till the at-st goes up to the mobile center then get bren in the mobile command center soon as he gets in the alarms sound and your troopers are attacking the artilery now you wont get slaughtered and use the turrets to take out the at-st now try and get the locals to help and luke is good at taking over the turrets. that sould do it
The force is strong with this one.