Liberate at least three provinces in Insula Dracon to unlock this story mission. In preparation for disabling the FOW protecting the Centcom in this region, you have to follow the pipes until you find the source. While following the pipes inside the cavern, you’ll find a couple of patrol boats and a small squad of foot soldiers in the end of the cavern. Destroy them all then follow the pipes underwater.
Wait for Dimah to open the gate then swim to the next area. Open the gate and destroy all marked targets inside. Once done, exit through the next gate to complete the mission.