ONI Alpha Site

Objective 1: Arm all charges on bridge
Start the mission on a bridge with friendly forces on one side and Covenant on the other. Activate the three remaining charges on the bridge. If quick, you can do this before engaging enemies. Proceed to the UNSC forces at the end of the bridge.

Objective 2: Use detonator in watch tower
After crossing the bridge, climb the ladder into the watchtower on the left. Activate the console at the back of the room. A sniper rifle is available in the tower. Exit the tower and clear any remaining Covenant forces. Proceed down the ramp and under the wall into a large open area at the foot of the ONI building.

Objective 3: Defend inner courtyard
Upon entering the area, a phantom will drop off Covenant troops, including Hunters, Brutes, Grunts, and Jackals. Target the Hunters' weak spots on their backs first. After eliminating them, deal with the remaining forces. As you ascend the first flight of stairs, phantoms will deliver more troops, including Brutes and Wraiths, to the courtyard. Retreat slowly up the hill while engaging enemies. Join the UNSC forces at the top of the stairs below the ONI building and defend the area, watching for flanking enemies coming up ramps on the sides. After a third phantom drops off more troops, continue defending until Dutch tells everyone to run inside the building.

Objective 4: Retreat, defend ONI building interior
Enter the ONI building and make your way to the central platform. Enemies will attack from four directions. Initially, they will come from the right-hand door (Grunts, Jackals) and then the left-hand door (Grunts, Jackals, Brutes). Watch for suicide Grunts. Use the plasma pistol's overcharge to strip Brute armor. After clearing the initial waves, focus on the two doors leading outside where phantoms will drop reinforcements on balconies. Use similar tactics: prioritize smaller threats, watch for flankers, and use explosives or the plasma pistol combo for Brutes.