2) Eliminate Outpost
The game should automatically create an auto-save once you've gone closer to the enemy base. I would recommend that you plan your next moves very carefully before attacking any of the surrounding soldiers. First of all, you should consider ordering your sniper unit to go west. He should have a nice view of the base from there (#1). You could also order him to hide behind some of the smaller buildings, because he would be safer there. The sniper should automatically take out at least two enemy units (#2).
You, on the other hand, should go to your right. There's a small passageway in front of you (#1). Order your men to hide behind a larger cover (#2). I wouldn't recommend allowing them to lean out or stay in the open for too long. You should also create a quicksave here, because you'll take part in some challenging battles in a short while.
Now you will have to provide some sort of an assistance for your sniper. Attack some of the visible enemy units (#1). You will be attacking these rebels from the left flank, so it shouldn't be a problem. Nevertheless, don't leave your cover unless you want to get shot. Additionally, some of the enemy soldiers may try advancing to your position (#2). Thankfully, you'll see them on the tactical map.
Don't leave this area just yet, because more enemy units will appear near the main encampment. Try killing them from a larger distance (#1) or at least distracting them in order to allow your sniper to kill them. Make sure that your teammates are safe. You could also turn right and take out more enemy units. They are standing closer to a large bridge (#2). Just as before, don't risk too much, especially if you're taking on larger groups of enemy units.
The last group of enemy units should appear in the central section of the encampment (#1). I wouldn't recommend changing your tactical approach. Try distracting them or kill them from larger distances. You will also have to watch out for your sniper, because one of the rebel soldiers may try to surprise him from the left flank (#2). You would have to kill this guy as soon as possible. Once you've killed all rebel soldiers, you will receive new orders.