The last attack is going to happen from the east. Thankfully, it's going to be a much smaller assault (#1). If you're lucky, your sniper will probably kill all enemy units and the enemies won't injure any of your teammates. You will have to wait for the EMP pulse (#2). This will allow you to disable the device. Don't worry that you can't hear your colleague. Everything will get back to normal in just a few seconds.
4c) Destroy the enemy helicopters (You will have to destroy two enemy helicopters in order to ensure a safe extraction. Follow my instructions if you want to finish up with this task quickly and without any major problems.)
Immediately order your men to hide behind the nearest building. Enter it and head on to the balcony. The helicopters will arrive from the south (#1). You shouldn't have any problems spotting them. Choose the ZEUS rocket launcher from your inventory. Zoom in and wait for the launcher to lock on a target (#2).
Fire the missile. You will probably have to wait for a few seconds, but eventually one of the gunships is going to be destroyed (#1). QUICKLY start aiming at the second gunship. You will have to choose the ATTACK option from the menu (#2).
One of your teammates will use his rocket launcher. You must be patient, because it's probably going to take about 10-15 seconds. After that, the second gunship is going to be destroyed (#1). Wait for some new objectives to be displayed on your screen (#2). As you've probably suspected, you will have to evacuate from the map by reaching a nearby extraction zone.
4d) Get to the helipad for extraction (This is going to be a very obvious task. Your goal here will be to reach a well defended extraction zone.)
The landing pad is going to be located to the west (#1). I'm sure that you won't have any problems finding it. Sadly, enemy troops have arrived in the area, so you can't reach the extraction zone right away. Start shooting at the visible enemy units. Most of the rebels will appear near an upper balcony (#2). It should be fairly easy to find them.
Once you've dealt with the first group, start moving towards this new base (#1). The rest of the team (including the sniper) should be following you. Turn left, so you'll be moving south-west. You will probably encounter a few soldiers along the way. Find a small tunnel and use it (#2).
Be careful, because one of the enemy soldiers may be hiding just around the corner. You will have to secure this entire area (#1). Once this is done, head on to a nearby staircase (#2). You will have to reach the roof of this building. Go left.
You shouldn't encounter any additional problems here. The landing pad is going to be located in front of you. Take a seat inside the gunship. Now you will only have to wait for the rest of the team to do the same thing (#1). Don't worry about new rebels (they may appear near the dam). Once you're in the air, this mission will end (#2). It's time for the final challenge of the campaign!