Run straight ahead to the hostile camp (#205). Hide behind one of the containers and start eliminating the opponents. An armoured vehicle will show up (#206) - if it's not destroyed, you won't get any further.
To get to the vehicle unnoticed you will have to use smoke grenades (#207). Then you will be able to plant the C4 on it (#208). When you get to a safe place, detonate the explosives.
Keep going and you will get to the building from which enemy is shooting at your allies. Hide in one of the garages and look at the nearby container (#209). When you get there, walk around it and you'll find a perfect spot from which you can eliminate the enemies (#210), When it's done get to the building. One of the soldiers will blow up the gate (#211).
You're almost there - all you have to do is destroy two armoured vehicles that won't let you go any further. There are two ways of dealing with them. You know the first one: you throw a smoke grenade and plant the C4 (#212). The other one is simpler: just pick up any RGP and use it on the vehicles (#213). It doesn't matter which option you will choose. What matters is that the 2 vehicles will turn into piece of junk.
When you get rid of the vehicles, kill ale the soldiers that are still alive and wait for the silo to open . Grab the line (#214), to go down to the base.