Mission 1 - Sierra 117

Walk It Off

Follow your team until you come to an opening with a waterfall. Once you reach the entrance into the clearing, a Covenant Phantom appears and drops the first enemies you encounter. Follow the path up to your right, and engage the troops in the cement bunkers to your right.

After you have finished off the first wave, a second wave appears, dropping from a Phantom that appears at the little waterfall in front of you. Kill this wave and cross to the other side of the river via the rocks along the waterfall, and kill the third wave of troops.

Note: Try killing the Brute first as this sends the Grunts into panic mode.

After dispatching all the troops in the immediate area, follow your team through the cave tunnel marked with a red flare.

Emerging from the cave, you'll come across a horde of sleeping Grunts. As instructed by your squad, take out as many as you can with a melee attack. (You'll kill about five Grunts before they wake up).

Then, prepare yourself for heavy resistance -- Jackals, Grunts, and Brute Commanders. I recommend a pair of Brute Spikers, as they do considerable damage to even shielded enemies when used in tandem.

You and your squad will keep moving towards the Sgt., entering a small ravine. As you enter the ravine you will see a Brute holding a Marine by his throat above you. If you are quick enough, you can kill the Brute and rescue the Marine, bolstering your own forces.

With your new teammate in haul, make your way up and around onto the upper area where the Brute was, then enter the large cave marked by a red flare. A vision of Cortana flashes on screen. Follow the chain of red flares until you make it to the end of the tunnel.

Charlie Foxtrot

You'll find the bodies of Marines as you emerge from the cave. Search them and you will find a Battle Rifle.

Now that you have the Battle Rifle, continue forward until the path drops off. Ahead of you by the river are several enemies fighting a pair of Pelicans. Up on high ground, use the Battle Rifle to take them out, then advance to their location on the river.

Approaching the river, you'll see a pair of Banshees swoop in and down the Pelican that Sgt. Johnson is in. Although you've reached the river for evac, your evac has been taken out, resulting in a new objective.

Objective: Find Johnson's crashed Pelican

Kill the enemies fighting the Pelicans, then move into the ravine to meet your allies. With only a few steps into the ravine, you'll receive fire from Jackals with Carbines along the upper walls of the ravine, but they're easily spotted because they'll flash a purple light while aiming at you.

Move along the ravine, dispatching the Jackals and other ground forces, until you come upon a point where you see Marines fighting. Turns out they were aboard Johnson's Pelican! You've found the crash site.

Objective: Find Johnson before he's captured

Fight off the forces attacking the crashed Marines, including the ones dropped in by the Phantom, then collect the Sniper Rifle and ammo by the downed Pelican.

With your newly found Sniper Rifle, head back the way you came, towards the cave with a red flare by its entrance surrounded by your troops.

Enter and move through the cave, down its path, until you come to a cliff overlooking an enemy installation. A cut-scene ensues about an imprisoned Johnson, prompting a new objective.

Quid Pro Quo

Objective: Rescue Johnson and his squad

Take out as many troops as you can from your high ground position. Also, several troops sit right below you on the other side of the dock to your left.

Drop down and proceed forward to the bridge that allows you to cross to the other side of the dock. You will have to fight several Brutes on the bridge, including a commander complete with Gravity Hammer. Kill him and take his Gravity Hammer.

Use the Gravity Hammer to kill the remaining forces standing between you and Sgt. Johnson's cell. Free Johnson, drop the Gravity Hammer for a different weapon, and prepare for your new objective.

Objective: Stay alive - Pelican inbound

Two Phatoms will come in and drop off several troops. Finish them off and then join Sgt. Johnson and the remaining Marines back on the bridge between the docks. Jump on the Pelican and the mission is over