Ghost Town
Objective: Destroy first antiair Wraith
The mission starts with you in a convoy of Warthogs. Enjoy the ride, for now

At the outpost, you must proceed through the door by holding the RB button.

Enter the building and walk up the staircase, then make a right at the top, and another right at the next corner. Follow this path until you find the open doorway into the next room.

When you're in the room blocked off from the rest of your marines and the Warthog, find the controls of the door and let them in. The controls are along the catwalk to the right of where you've entered the room.

Once your Warthog enters the room, mop up the remaining forces, and open the door with the green switch.

Move down the hallway until you come to a Brute on a Ghost. You and your Warthog ally will make short work of him. Open the door that he was guarding and then hop on the unmanned Ghost behind you. Proceed out the door.

As you exit the door you will see a vast open area. Don't race off onto the walkway. Instead, take a left when you're out the door and stick to the upper perimeter of the area, in order to reach the center platform, where a Phantom drops off a number of ground troops. Hop off your Ghost and eliminate the enemy troops.

With all the Covenant ground forces destroyed, proceed to the roof of the building, where the Phantom dropped off enemy troops, and pick up the sniper rifle up there. Use it to kill the gunner of the first antiair Wraith.

Get back down to the Ghost, and drive off the upper area and down to the ground.

On the ground you'll fight four enemy Ghosts. Eliminate them and then drive up to the antiair Wraith. Since the gunner is dead, hop off your Ghost, jump onto the Wraith, and plant a grenade. This will destroy the first antiair Wraith, completing your objective and prompting a new one.
----------------------------------------------------------------------------------
Objective: Destroy all other Wraiths
Proceed to the far side of where you came in and destroy the Wraith. You can sneak up on the Wraith by coming up the ramp near it. Climb onto it and plant another grenade.

Enter through the door just past the destroyed Wraith, and then take an immediate left. Enter the door ahead of you and go up the stairs. At the top of the stairs is a large grouping of Brutes and Grunts. Lob grenades until nothing moves, and then proceed back down the stairs and through the opening doors.

Enter the next room and proceed to the large set of doors straight ahead. Wait until the rest of your forces are fully in the room, including the Warthog, and then hit the switch that will open the doors to the next room. You will be ambushed by a large group of Drones. After taking them out proceed down the hallway, where the rest of your allies are.

After regrouping with the rest of your forces, you'll be prompted to drive with a squad of Mongooses, each with a soldier equipped with a rocket launcher. Take control of a Mongoose and proceed through the opening doors.

Through the doors you'll enter a large dried lakebed. Your target: the remaining two antiair Wraiths. Don't worry about staying too close to them or the various Ghosts/Banshees guarding them; just drive without stopping. The gunner on the back of your Mongoose is a crack shot, so as long as you're both alive, he'll make short work of all the enemy vehicles.

After destroying the enemy in the area, a Pelican drops in another Mongoose with a copilot equipped with a rocket launcher. Then, as a Scarab moves into the area, you will enter a new chapter and be given a new objective.
--------------------------------------------------------------------------------
Judgement

Drive around the Scarab, staying out of its front arc. The Scarab also has a secondary gun on its back, so you must keep moving. If you get flipped, just get back on your Mongoose, and keep moving again. And don't worry about damaging the Scarab; you're computer assistants will know exactly where you need to hit it.
Keep moving.

Once the Scarab falls to the ground, you must board it and deal a death blow. Jump into the back portion of the Scarab, proceed up a level, and then shoot the Scarab in its core appearing like an energy shield. Shoot the core twice, then jump off the Scarab before it blows. With the Scarab destroyed, you are given a final objective

Objective: Neutralize the antiair cannon
Pelicans come in dropping an Arbiter to the ground. Head to his blue arrow and then follow your squad through a series of hallways that lead to a truck-loading area. Now, fight through the two large rooms against a series of Brutes. Destroy them and prepare for the third room

Fight the pair of Hunters when you enter the third loading dock. Close the gap between you and them, disabling their ability to use their cannons.

Use a Bubble Shield if you have one, which will allow you to pop out and hit the Hunters with grenades.

Once you've killed the Hunters, don't go out the doors that they came through. Instead, head up the stairs to the left of the door they came through, where you'll find a sniper rifle.

Use the sniper rifle to take out several enemies, including a Brute Commander with a Gravity Hammer. When you've exhausted the sniper rounds, jump down, take the Gravity Hammer, and follow your troops.

Using the Gravity Hammer, smash through the remaining troops between you and the antiair cannon.

Kill the Covenant forces around the gun and then shoot the blue orb that appears beneath the gun whenever it fires off a shot; a few Plasma Grenades ought to do the trick.

The mission is over when the gun is destroyed.