Head up the pathway to meet marines under fire from Brutes, Grunts and a Wraith. Laser the Wraith, be sure to aim where it launches its mortar, when destroyed, assist the marines against the infantry, a few grenades should fry them. Commandeer the driver's seat of a warthog (Or gunners, if you're a good gunner). Head down to the destroyed Wraith to meet a Chopper, a pair of Ghosts and another Wraith. Your first priority is the Chopper, so avoid getting close to it, as its blades can easily rip an overconfident player's warthog to pieces. Give the gunner a clear shot at the operator or laser it. You now have the choice of the Chopper or the Warthog, if it is still intact. To take care of the wraith, simply shoot the shiny projector at the top until it explodes.
The laser is much more effective on the wraith than the Ghost, Warthog or Chopper. destroy it and then mop up any stragglers. Head to a small pathway to a ramp and head down to another area.
Near the sniper tower, there is a grunt armed with a fuel rod. He can be a huge threat to your vehicle, so be sure to splatter him or give him a few bullets to his head. Banshees will strafe in this part and Shade turrets line the wall. Have the gunner eliminate the banshees or laser them, but conserve your laser ammo, you never know when you need it. The Shade turrets aren't a big threat, simply ram them at top speed, they don't stand a chance against the battering ram of any vehicle. Doing this can also cause your stamina and possibly your health to drop. Don't stop for anything unless absolutely necesscary.
Head through the narrow pathways to reach another marine squad under attack. You can find health packs, extra ammo and another warthog. When you get the warthog, be sure to have the shotgun seat empty because one of the marines is carrying a laser and they are extremely useful at eliminating enemy Wraiths and Choppers. Since they never deplete charge, they have infinite ammo! Once the area is cleared, head to the building the Wraiths came from, toward the elevator. Stop by the building to find a nearly unnoticed dead Brute to pick up a pair of useful firebombs.
When the elevator collapses, rush past the bridge and up the pathway, stop for nothing. When you reach the Covenant LZ (the big purple base) run over the LZ repeatedly to splatter all enemies, then focus on the wraith. Pass the destroyed tank to go up another series of hills to reach the final area. The area is filled with Brutes, a chieftain and a Wraith. You can destroy them all or move on.
There will be a huge gap that you can see a street, jump through the gap and the mission ends.