Mission 2 – Winter Contingency
Mission starts at 0:00:14
in the walkthrough video below.
Alright, this is where the rubber meets the road. First thing’s first, I will warn you: DO NOT enter any vehicles during this mission up to the point where you get into the evac choppers. Doing so will net you the "They’ve Always Been Faster" achievement at the moment of evac toward the latter 1/3rd of the mission.
From the start of the mission, make sure you’re taking the time to shoot any of the ostrich-looking wildlife, named MOAs. Shooting 7 of these will get you "Keep It Clean". There are more than 7 during the mission so this shouldn’t be a problem. This will be your first achievement if you get the 2 MOAs at the start and the next 5, provided you run past the first enemy encounter the way I do in the video.
You’ll reach a building near the beginning with an Elite and several Grunts in it. This will be your first actual fight if you follow my path in the video (skipping the first group of enemies before this). Inside the building is a health pack. Let the enemies lower your shields until you take some health damage, then kill them. Head inside the building to use the health pack and net the "Doctor, Doctor" achievement.
From the start, stick to your human pistol until you’ve amassed 10 kills with it. You can drop your Assault Rifle in favor of a covenant Plasma Pistol to do PP EMP + headshot combos to take out elites. Just make sure the kill shot is with your pistol until you reach 10 kills with it to unlock "I See You Favor a .45". You’ll unlock this right around the same time as the building above with the health pack, provided you kill all of the Jackals, Grunts, and the Elite leading up to/in this building with it.
One of the buildings you have to check for survivors will have a DMR in it. If you follow the path I do in the video, this will be the final building you come to of the three, and thus where the evac choppers will meet you. There’s a health pack in this building too. For reference, this particular building is sort of built into the side of a hill, with two levels. If you miss the DMR here, you can get one in the building you land at and get out of the evac chopper, where enemies are being dropped off from dropships outside. Use the DMR for 10 kills to unlock "An Elegant Weapon".
Also in the same final area where you're holding off against Covenant and waiting for the evac helicopters, you'll have some Marines nearby. Trade weapons with one of them to get the "Swap Meet" achievement.
When the evac helicopters arrive, you’ll unlock "They’ve Always Been Faster" as long as you haven’t entered any vehicles up to this point in the mission.
Finally, after the next section defending from waves of enemies and making your way through the building at the end of the mission, you’ll unlock the story-related unmissable achievement for completing it on normal or higher.