Camp Omega is about to experience a military raid. Before it does, Snake needs to take out three anti-aircraft emplacements to ensure things go smoothly.
The first emplacement is right in front of you. Use your binoculars to spot and tag any guards in the area. Once tagged, move up and wait for the lone guard to walk off. Approach the AA and plant a C4 charge onto it. Do not blow it up just yet.
You can choose to plant C4 at the emplacements in any order you wish. The problem is that the carrier conducting the military raid has been detected, causing guards to be on alert. Expect things to be a bit more difficult going forward.
Once the first C4 charge is planted, head straight forward in the same direction you were facing to start the mission. Watch out for the guards. When you reach a fence, go prone and wait for two guards to move out of the area. You should be close to the AA gun near the lookout tower. Scale the fence when the coast is clear, sneak up on the guard by the AA gun and take him out with a tranquillizer dart. Hide the body off to the side and set your second charge.
Keep an eye out for the patrolling guard by the fence where you entered this area. Wait for him to move away and get in the nearby truck. Follow the road around and park the truck under the bridge, next to the third AA gun. Rather than approach it and plant C4, throw a grenade to destroy the third gun. This will leave you with three pieces of C4, all of which are necessary for the next portion of the mission. Be sure to detonate the first two charges you planted to destroy all three emplacements.
Place three C4 charges on the ground at the front of the truck. Go prone in the bushes off to the side, making sure to leave enough room that you're not killed by the upcoming explosion. When the armored vehicle approaches, detonate the three charges to complete your objective.
Turn and head down the road towards your objective. You now have three minutes to escape. Even if you only have 30 seconds, you’re fine. Just sprint toward the extraction point and board the chopper to finish this side mission.