After short walk, you'll encounter new enemy: Gunner. Get rid of him and kill all Stroggos in the neighbourhood. Walk straight ahead. Clear the area of enemies and go through the next door, where you'll meet Rhino squad's soldiers (#15).
You'll get the Shotgun. Get ready for some action. Walk into the courtyard (#16) with allied soldiers (there is a big machinery). Cover behind the crate and concentrate on eliminating opponents. During the fight beware of loosing medic - you'll need him few minutes later (especially on higher difficulty level). When the area is clear of enemies, go with your team to another location.
Inside, be ready for another firefight. After eliminating the Stroggos, go inside the elevator (big hatch), wait for the rest of your team and travel down. You'll get to big hall, which is growing with enemies. They'll also jump down from higher levels, so be prepared for a tough fight. Remember to cover medic and engineer (#17 - he can supply you with armor). After the battle, team leader will try to destroy reinforced glass. He won't make it and it's your job to find another way to destroy it.
Recover heath and armor and walk through the doors, located opposite the reinforced glass. Kill all enemies, find the ladder (#18) and climb up. Push the button on electronic panel (#19). Eliminate new opponents and move to the other side of the new walkway.
On lower level, you should see the rest of your squad. Push the button (#20) and wait for a while, until the big cannon comes down. On the right side, you'll see a tunnel, leading to elevator. You'll join the team. Activate the panel (#21) - it'll destroy reinforced glass. Move ahead.
Another big hall awaits you. Recover health and armor (if possible), and push the green button (#22), located near the bridge. Keep yourself on the right side and eliminate as much enemies as you can (they'll try to walk over the bridge).
After the fight, walk on the bridge. There's a ladder (#23), right next to doors that will lead you to some useful items. Go back to the gate, walk inside and kill all opponents. Another door will lead you to an elevator (#24). Walk inside to finish this level.