You and Woods will be looking for a double agent and may need to carry out his mission. Patrol choppers will appear above, so quickly hid near the pipes ahead. Duck down and do not fire, or you will be quickly discovered. Once they pass, follow Woods and you'll steal uniforms from a few guards.
Meet up with Brooks and Bowman and let them distract the remaining guards. Go with Woods and kill the enemies inside the next building. With the tight corners, your grenades will be a great means for disrupting groups and getting in surprise kills. Still, your rifle is the best bet for killing most enemies.
Move to the roof and kill the enemies around. Some will not even notice you, allowing you to sneak up and kill them with quick melee attacks. Afterwards, meet up with Woods again to gain an explosive crossbow. Use this weapon to support Bowman and Brooks as they storm the next base. Zoom in with the crossbow and destroy the trucks below.
Hook up and swing down to rescue the double agent: Weaver. There will be a bit of slow motion, so you can quickly execute his guards. He'll thank you and join up with your squad. In the next area, Brooks and Bowman will split off to the lower level. Stay by Woods and Weaver and take the upper section.
Keep using your default rifle, as its attachments and iron sights are excellent for the on coming fire fights. Communist soldiers will enter from below and group up. Use your grenades to take them down and clean up the rest with your gun.
You'll come to the launch center. Use the one screen commands to set up a bomb and kill the scientists inside. You'll be too late to stop the rocket from taking off. Move back outside and grab the missile launcher on the other side. Aim for the rocket and blast it out of the sky. You have some control over your own payload, so aim high and steer to get a good shot.
Follow the rest of your team inside and clean up the last of what remains inside the fortress. The enemy will make use of grenades themselves, so don't step out too quickly and blow your feet off. Instead, lay back behind cover and take them down when the fury dies down. There are a lot of foes, so if you run low on ammo be sure to steal a gun from their cold dead bodies.