Objective: Secure perimeter defenses
Proceed down the staircase through the hallway, and a soldier will open the door for you. Head outside, up the stairwell towards the hangar, following your troops. Now open the steel door by pressing the RB button on the control panel left of the door. Continue through the next open door, towards the main hangar, and open another door towards your objective.
Objective: Neutralize hostiles in the hangar
To the left of the exit will be an encounter with Covenant Grunts and Jackals. Continue forward towards the oil tanker truck and defeat the Brutes in the doorway and continue forward.
Use the scope on the Battle Rifle, and shoot the Jackals at the end of the hall while your squad cleans up the rest of the Covenant forces. Proceed down the hallway, and take a left through the open door. There will be a small room with doors to the left and right.
We recommend that you go through the door on the left, since it not only provides more options for cover from the forces inside the hangar, but also gives you a nice advantage point on the stairwell the Grunts use to get to your position
Once you've killed the initial Covenant forces, or when the dropship retreats (whichever comes first), make your way to the right side of the hangar and use the turret. Detach it and carry the turret to the hangar deck, using it on the remaining enemy forces.
Another dropship will arrive to provide you with more resistance. With the turret in tow, aim at the dropship's plasma cannon at the very front of the ship and destroy it. It will retreat, allowing you to concentrate on cleaning up whatever Covenant forces remain in the hangar. Now proceed back to the ops-center at the start of the level.
Objective: Get back to ops-center
On your way back, you'll encounter a swarm of Drones. It's recommended you equip your Assault Rifle and take out these flying pests with short controlled bursts. Once they're killed, continue on your way to the ops-center, where you'll give the Covenant a small but awesome gift: a bomb.
Objective: Rescue marines in the barracks
Before you can setup the bomb, you'll need to rescue marines captured by Brutes in the barracks. So get your heavy weapons ready such as shotguns, plasma grenades, and take these guys out as you enter the doorway to the barracks. When you first enter, you'll find the brutes distracted and taking orders from the Cheiftan. Use this to your advantage. The brute "captain" with green armor is armed with a brute shot, which can be a real pain to deal with on legendary. While he's kneeling receiving his orders, try to take him out first with a well-timed plasma grenade stick. This will make this encounter much, much easier. Of the different enemy forces in the barracks, the strongest is Brute Chieftain, who carries a Gravity Hammer. Don't get too close to him, because the Hammer will knock you on your butt in just one or two hits. A combo of grenades and shotgun will take care of him, though.
Swap out your assault rifle for the Gravity Hammer on the Brute Chieftain's body. Continue up the ramp and through the open door. Walk down the hallway and drop down the shaft in the ground. Switch to rifles and fight the drones in the air chamber. Proceed towards the large air vent shaft, drop down (don't worry, you won't get hurt) to the bottom of the shaft and go through the doorway to rendezvous with the Arbiter. Finally, you'll enter the barracks.
Your objective is simple: save the marines in the barracks, and then evac via the landing pad. Equip your Battle Rifle and dispatch the Brute choking one of your soldiers. If you manage to save this solider, he'll retreat and pick up a rifle for himself, providing covering fire. Kill the Brutes in the barracks with the Battle Rifle and the Gravity Hammer.
The Battle Rifle will take care of the Brutes from a distance, while the Gravity Hammer works great for the up close and personal attacks against the Brutes. The Hammer has a limited amount of hits to it, so once it's done you should find another weapon to swap out. Plus, the Arbiter will help you out a lot in this section, a bonus considering he can't die no matter how many hits he gets -- use him to your advantage. After you've squashed the Brute resistance, proceed through the exit door (follow the Arbiter to this location) and outside to the elevator lift towards the landing pad.
Objective: Evac via the landing-pad
On the landing pad, you'll be ambushed by a dozen Brutes in jet packs. Wait for them to land before opening fire, since it takes the jet pack a bit of time to fire their thrusters and propel the Brutes through the air. When all the Brutes are dead, a Pelican arrives to pick up the troops and to bring them to safety. Now, go back to the ops-center again, because the Brutes have managed to disable the bomb. It's up to you to make it back there and rearm the bomb.
Objective: Return to ops-center, arm the bomb
On your way back to the ops-center, you'll come across a Grunt operating a plasma turret. Kill him and take the turret in order to dispatch the Covenant forces easily. Continue towards your waypoint marker to the ops-center. Activate the bomb and escape!
Objective: Escape - Find the elevator in the hangar
Ditch the plasma turret before you begin your escape, since it will only slow you down. Equip a shotgun, a Battle Rifle, or an Assault rifle, and make your way to the hangar bay (yes, the same one from earlier). Follow the on-screen waypoint marker to the maintenance elevator and escape to the next level.
