Speak with Dimah by Corda Dracon, then take out the hordes of enemies throughout the area. The first engagement takes place to the northwest, so head to the marker and assist the rebel plane on the runway. Your goal is to make sure the plane takes off, which means you need to handle the enemies attacking it.
Take control of a jet at the airport and head to the next destination marker. It’s your job to protect the boat on the water. You need to defend it against bombardment from aircraft above as well as other enemies in the area.
The last area of contention is to the east. Head over to the boat just outside the water gate, then take the boat inside when the gate opens. Dock the craft by the generator in the back of the first room, then take out the generator and search for a tunnel in the water. Swim through the tunnel, coming up for air when you reach each air pocket, then grapple up and open the door to the next room (press the red button).
There are two more generators above that should also be taken out. Grapple up to them and do your worst, then leave the cave through the tunnel above. With all three generators destroyed the base is done for and the mission is complete.