Halo: Spartan Assault

You will earn this in the Campaign. The game has several 'Operations' (these are like chapters) and each Operation has several missions. Operation A has 5 missions. Just complete all 5 missions and the achievement will unlock.

To earn this achievement, you must beat all five missions in Operation A. In this solution, I will give tips to help you complete each mission with a gold star (which in turn will also earn you an additional achievement if you get all gold stars), and tips on how to finish all three assault ops that come with each mission (which will also earn you another achievement for completing all 90 of them). I've separated both sets of tips into different paragraphs in case you're only here for certain information.

Mission A-1 Gold Medal: A fairly straight-forward level, the key here is speed. You'll need to get 35,000 points for the gold medal, so you'll immediately want to run to the left and kill the Grunts that spawn in with the Magnum. Once those are done, do a 180 and fight the Elites on the other side of the map. You can usually kill these pretty fast by shooting them a bit with the Assault Rifle, and then hitting them with a melee. Chaining your kills together will also give you a higher medal score, so keep that in mind from now on.

Mission A-1 Assault Ops: The Assault Ops for this mission require you to kill 20 Grunts with the magnum, another three Grunts with grenades, and you will also need to kill 20 Elites in whatever way you can. These objectives are fairly easy compared to what we'll encounter later in the game, so savor these moments. Get the kills you need, then restart until all three objectives are complete.

Mission A-2 Gold Medal: Once again, the thing that's going to get you the gold medal here is speed. This time around you need 45,000 points. As you go through you'll encounter Grunts and Elites. The methods described before are best for killing them quickly. Once the mission starts you'll want to run right and you will encounter three Grunts and an Elite, kill them before they can use either of the Shade Turrets close by. Moving up from here is the first turret you have to destroy, use grenades, and then mop up the remaining enemies, if there are any. From there you'll need to go right and past some barriers where you'll fight an Elite and five Grunts. Head up again and you'll find a weapons cache with some plasma grenades nearby. Grab those and use them to destroy the second turret. Just past this turret are three Grunts, one of which has likely climbed into the Shade Turret. Hijack it if you're close enough or use a grenade if you have an extra, whichever you find to be faster. Head right and you'll fight a pair of Elites and a pair of Grunts. You'll see the final turret to the left, but you'll have to go up and around to reach it. Guarding the final turret are two Elites and a Grunt. Kill them and shoot the fusion coils next to the turret to blow it up. Now back track a bit to where the Hornet is, if you're having trouble finding it look at your radar and head towards the yellow dot. Before you board, another group of enemies should spawn just north of the Hornet, so kill them for extra points.

Mission A-2 Assault Ops: For these you'll need to destroy two Shade Turrets with Plasma Grenades, kill 20 Grunts with the Plasma Pistol, and kill 40 Elites with the Plasma Repeater. Plasma Grenades can be found next to the second and third main turrets you have to destroy. The Shade Turrets don't have to be occupied, so keep that in mind. Grunts will drop Plasma Pistols, so after your first kill you can swap out a weapon for one of those. You'll find pretty quickly that the Plasma Pistol isn't super great, but don't try to weaken the Grunts first as pretty much everything else will one-shot them. The 40 Elites objective is the real kicker here. There are only about 8 or 9 Elites that appear in this mission, so you'll have to run through the mission about 4 times using the Plasma Repeater to kill them. If you're running low on ammo, there are Covenant weapon caches around this map for you to restock. Try to stay ahead of the marines, as they like to throw grenades and steal your kills.

Mission A-3 Gold Medal: This is an escort mission, so the time bonus isn't really an option here. You'll need 75,000 points for this one, so what you'll want to do is focus on chaining kills. Move ahead of the Wolverines and kill enemies that have already spawned in. You should hear one of the Wolverine operators letting you know when they're taking damage, so when this happens, back track and kill the enemies that are coming in from behind. Do keep an eye on the Wolverines' health, if one of them is destroyed the mission ends. Also be weary of moving vehicles from now on. If a moving vehicle touches you, you die. If ammunition becomes a problem for you, use the Shade Turrets around the map.

Mission A-3 Assault Ops: You have to destroy 3 Shade Turrets with a Plasma Pistol, kill 30 Elites with an Assault Rifle, and kill 40 Grunts using a Shade Turret. For the 3 Shade Turrets, just ignore the objective and find a Grunt to obtain a Plasma Pistol, locate a Shade Turret, chuck a grenade at it to lower its health, then fire a charged shot from the Plasma Pistol until the thing blows up. Repeat two more times. To my knowledge there aren't too many Elites on this map either, so you may end up having to play the mission 3-4 times in order to get the 30 kills you need. As for the Shade Turret kills, there are plenty of Grunts and four Shade Turrets to be used. If an enemy is occupying one, just hijack it instead of trying to kill them.

Mission A-4 Gold Medal: This is a pretty good breather in terms of difficulty, even though you need 105,000 for gold. You're given a Wraith to use right at the start. The level design is pretty linear so I'll skip the directions. Along you way, you will want to focus fire on other threats like Wraiths and occupied Shade Turrets. After they're out of the way, mop up whatever remains and move forward. It should be noted that just barely hitting an infantry with your vehicle will kill them instantly, so don't bother wasting time shooting a foot soldier that's on the main path. Before you finish the mission, get out of your Wraith and destroy it if you're still short of the points you need.

Mission A-4 Assault Ops: Kill five Elites with Plasma Grenades, 30 Grunts with a Plasma Repeater, and 15 Wraiths with a Wraith. For the first two AO's, destroy the barrier with the Wraith and then head out on foot. You'll start with three Plasma Grenades for the Elites, and more can be found near to the left of the main path just before the end of the mission if you don't want to restart. There are a decent amount of Grunts to be found in this mission, but you will likely have to play it around two or three times to get this one done. As for the 15 Wraiths with a Wraith, that can be done just playing the mission as you're meant to. Keep in mind that as with Shade Turrets, unoccupied Wraiths do count towards this, so make the most of it.

Mission A-5 Gold Medal: This is a hold-the-line mission where you'll be tasked with defending the area for a set amount of time. That being said, there's no reason to aim for a time bonus. Instead, focus on chaining kills together to hit the 115,000 you'll need for this mission. Once it starts, go up and swap abilities for the Regeneration Field. I would recommend using the turret to the northwest corner of the level for a bit. Burst fire it for best results, and get off of it once its health is low or enemies start coming in behind you. There are a fairly decent amount of enemies that spawn in over time, so as long as you're doing your best to keep your kill chain up you should be okay. Towards the end you can hijack a Wraith, but it will take damage pretty quickly so it's up to you if you want to risk that. You will spawn with a shotgun, which I would use strictly for Elites, and save the Magnum and grenades for the Grunts.

Mission A-5 Assault Ops: Kill 15 Grunts with a Machine Gun turret, kill 100 Covenant with the Shotgun, and destroy 4 Wraiths with a Magnum. 15 Grunts with the Machine Gun is a piece of cake, and you'll likely get it on your first run of this mission. While getting 100 kills with the Shotgun is a bit of a grind, I would just use it until it's out of ammo and then restart until you've got it. That's right, you don't have to finish the mission for progress to count. As for the Wraiths, it really isn't as difficult as it sounds. Only about two Wraiths spawn in towards the end of the mission, but there is a catch to this Assault Op. You don't have to only hit the Wraith with the Magnum. Bring its health down with a grenade (maybe two), or the Shotgun, or one of the Machine Guns and then switch to your Magnum to finish it off. You definitely want the Regeneration Field while you're going for the Wraith kills, as you can lose health pretty fast.

And that's it for Operation A. Happy hunting!