There is a switch on a pedestal next to the doors. Jump on hill and then onto the pedestal and activate the switch. Go into inner part of camp. You should get 2 messages in each barrack. When all three are done, escape through sewer located behind the farthest barrack.
Sewer is big maze, no tricks.
When sewer is exited, you should see car in front of you. Enter sewer pipe off on the left. Head straight through sewer to bomb crater. Hk is in middle of crater. Go back to sewer pipe and escape through lower one.