Something to be on the lookout for is that you must get a single kill with every single weapon in the game. Some only appear once, while others are very common. Once you get a kill with your final weapon (I will show them throughout the walkthrough), you will unlock:
MISSION 1: F.N.G.
Intel to collect: 0
The first mission serves as a tutorial. During the first part, you'll need to follow the instructions on-screen. The second part however, it a bit more trickier. It's an obstacle course which requires you to beat the record time. There are a total of 9 targets to shoot, and you'll need to throw two flashbang grenades (it will be mentioned when and where, pay attention). Also, having close to 100% accuracy rewards you an accuracy bonus that shaves 3 seconds off of your time, so make sure to actually hit targets efficiently. Once you've beaten the record time, you'll have the recommended difficulty set as "Veteran" as well as your first in-game achievement:
Now, if you thought it was hard to beat 19 seconds, then you're in for a treat. You must now complete the course even faster, beating the time of 15.1 seconds. Just remember to use the tips above and make use of the pistol, and you will eventually manage to complete this daunting task.
Head to the monitors for your first briefing to unlock the first story related achievement:
MISSION 2: CREW EXPENDABLE
Intel to collect: 2
The second mission is divided in three parts: the first one is being stealthy, the second is guns blazing, the third is running for your life. There are several miscellaneous achievements you can unlock here, as well.
At some point in this mission, you'll want to shoot an enemy once or twice (preferably in the legs) so that they fall down, but don't die. They should start attempting to crawl away in pain. Then, you should knife them using 
and unlocking:
At the very beginning of the mission, kill an enemy in the first room with the MP5SD (Weapon 1) and kill another with the Silenced USP .45 (Weapon 2). Then, you will go down some stairs and a drunk guy will stumble in front of you. Use a flashbang to blind yourself and knife him with (while still blinded), then go into the room that he walked out of and knife the two sleeping enemies. This will unlock:
and
Turn to the left of the bed and grab intel 1/30
Later in the mission, you will be in a small hallway with many pipes that wrap around to the right. Enemies will attack you once you head towards the right. Kill one of them with a grenade which is thrown by 
(Weapon 3). Then, all of your comrades will gather around a door and one will throw a flashbang through. Proceed through the door and turn right. In the middle of the area, at the bottom of the stairs, you will find intel 2/30. Kill the enemies around it and pick up an AK-74u. Replacing your MP5SD.
Proceed to the other side of the room, and walk through a small pathway against the wall to the left. An enemy will jump out and attack you. Shoot him to death with the newly acquired AK-74u (Weapon 4). Once killed, he drops the Desert Eagle. Now, you must kill 5 enemies with the Desert Eagle (Weapon 5) which unlocks:
In the room after the Desert Eagle room, you will enter a door to the right. Two of the first enemies in this next room drop an AK-47 and Mini-Uzi. Pick up both of them. Proceed to kill one of these last few enemies with each of them (Weapons 6 & 7).
The final checkpoint is once you get onto the main deck while running without a gun, however you can do the Veteran glitch any time after you grab the manifesto because there will be no more combat. Just remember to pause and check in the top right corner to make sure that you actually changed it to Veteran afterwards.
Now, all you must do is complete the mission. This will unlock:
If you are playing on "Veteran" difficulty (or did the glitch), you will also unlock:
MISSION 3: BLACKOUT
Intel to collect: 2
Onward to mission 3, a level that is still relatively simple.
New weapons you may find in this mission on dead bodies (Get a kill with each if you find them):
- MP5 (Weapon 8)
- RPD (Weapon 9)
- M9 (Weapon 10)
- RPG (Weapon 11)
- Skorpion (Weapon 12)
- Dragunov (Weapon 13)
- G3 (Weapon 14)
At the beginning of the level, you will spawn with an M4A1 SOPMOD and an M21 Suppressed. Equip the M21 Suppressed and kill the first enemy you see with a headshot (Weapon 15). Then, hurry up and shoot the enemy behind him in the head too. To the left of those two enemies will be another two in a small shack. Headshot those two also. This will unlock:
Enter the shack and pick up intel 3/30 to the right of the door. Now, proceed to the next area. You will come across a house with two enemies. Kill one with the M4A1 SOPMOD (Weapon 16) and kill the other with the M203 grenade launcher which you can equip by pressing 
(Weapon 17). Remember to loot bodies for any new guns, then proceed.
Later in the mission, you will walk through a burning house to kill troops being dropped in via helicopter. Use C4 to kill at least one of them (Weapon 18). To equip C4, press 
which allows you to throw it with 
. Then, it is detonated by pressing yet again. Then, try to kill at least one of them with the Claymore (Weapon 19) which is equipped via 
, then planted with . Anyone who walks in front of it will explode. Then, loot bodies again.
Eventually, you will reach the final building where Gaz will cut the power. Turn on you night vision with 
, then enter the building and clear out every enemy until you find the informant. Directly across the hall from the informant's room will be a bathroom holding intel 4/30 in front of the toilet.
You should get to the final checkpoint around the time you reach the room holding Nikolai (make sure you see 'Checkpoint Reached' at the top left before you save & quit). After that part, you just have to walk out to the helicopter, so you can beat it on Veteran with only 1 or 2 enemies to worry about.
Finishing this mission successfully will unlock
Completing this mission on "Veteran" difficulty will also net you
MISSION 4: CHARLIE DON'T SURF
Intel to collect: 3
New weapons found on a table (right before the first TV)/dead bodies:
- W1200 (Weapon 20)
- AK-47 Grenadier (Weapon 21)
- USP .45 (Weapon 22)
- GP-25 ( on AK-47 Grenadier) (Weapon 23)
Mission 4 involves multiple new weapons (listed above) and an annoying achievement being Your Show Sucks. You must destroy every single television in the level that is showing Al-Asad's speech and execution of the president from earlier.
Video Guide for Your Show Sucks (Courtesy of BradLeafsFan9):
You will start with an M4A1 which will be (Weapon 24) once you get a kill with it and an M9 which you can get a kill with if you didn't find it on earlier. Proceed into the first building and down the stairs. At the other side of the room will be the first television to destroy and in the middle of the room will be a table covered with weapons/weapon variations. Then, you want to enter the room to the back left from where you first entered. You can find intel 5/30 and your second television. After you find all of this, you may leave the progress through the building until you exit. You will go through a road half covered in barbed wire; immediately turn right and you should see a few enemies next to a car. Fire everything you can into the car until it explodes. Hopefully this kills two enemies (if not, just reload from checkpoint and try again) which will unlock you:
Once they die, turn left from the car and follow the right wall of the next area that has bunch of enemies to kill. Eventually there will be a little pathway out of the area. In front of you should be building to the right with an open door way and the path to left with a bunch of enemies shooting at you from the rooftops. Enter the door on the right and head upstairs. On a table in that room is intel 6/30 and in the back corner of that room is your third TV, so make sure it's destroyed. Leave the building and follow the pathway to the right where you'll encounter a road. If you look across this road, you will see a couple enemies firing at you from the top of a building. Go to the left of this building always looking to your right where you will eventually find stairs leading up to the roof. To the left of the top of the stairs will be intel 7/30 and your fourth TV.
A small bit later, you will breach a broadcasting station with your comrades. Immediately upon entering the building, there will be two TVs in the first room. There is one right above you to the left as you enter the doorway that was breach. The other is in the upper left corner at the other side of the room. In the next room that you enter, there will be another TV above the door that you use to progress. Go through that door and shoot the TV on the right side of the room that is facing you, then go to the door on the other side of the room and turn around. There will be a second TV facing you on a desk in front of you. Now, for the TV wonderland! You will walk through two more doors and enter a massive room full of TVs. Go into the corner directly to the left as you enter to find your first. Then, go to the room across the door from where you entered and follow that path until you reach another door with a TV that you must shoot above it. Look through that door and you should see another TV mounted on the wall to shoot. After destroying that one, follow the wall to the left to kill the final mounted TV. Now for the scavenger hunt. Search every single desk in the center of that room and destroy every TV showing the speech that you can find; just remember that missing even one voids the achievement and you'll have to restart. And, to finally finish this room, destroy the four walls covered in TVs.
A tiny bit later, you will regroup with a few of your comrades and head up some stairs. Look to the left wall of the first room you enter, and you will see one more TV. The only room left is the room that you breach in to end the mission. There are six TVs inside to destroy, but you must do it before your allies finish talking and end the mission. You will find one on a table connected to right wall from where you entered, two inside of the booth after that, one in the middle of the room, and FINALLY two on the left wall. Once you destroy the final TV, you will unlock the tedious achievement:
This is also where you can do the Veteran glitch.
For completing the mission on "Veteran", you will receive:
MISSION 5: THE BOG
Intel to collect: 2
Save your M4A1 Grenadier until the end of the mission; you will need it for an achievement.
Near the beginning of the mission, you will be sent up some stairs with Private Roycewicz. Hurry up the stairs past him and knife the enemy standing there. You will have saved Roycewicz's life and earned:
Now progress until you finish using a mounted gun to kill enemies on the other side of the building and you are told to advance. Head back where you came from and you should see two allies kicking in a door. Walk in that room and turn left to find intel 8/30.
Keep going in the mission until you are ordered to pick up a Javelin and run into the building to the left of where you entered the area. Climb up the stairs and walk out the door to the open roof. Now, you must use the FGM-148 Javelin (Weapon 25) to kill all four tanks on the bridge (three from the right, one from the left). The Javelin is locked on by aiming on a vehicle for long enough that there is a square in the middle with a crosshair through it. Then, press to fire. It will one-shot kill tanks. Once all four are killed, you will unlock:
Now crouch through the slightly cut open fence to progress. Follow the pathway making sure to always hug the left wall. Eventually you will reach a fruit crate placed diagonally in a corner. Look behind it to find intel 9/30.
Now you can get the achievement to kill twenty enemies with explosives in a single mission using your good 'ol M4A1. Once you reach the tank (War Pig), turn left and use your grenade launcher to kill as many enemies as possible. Once you kill twenty with explosives, you will unlock:
If you don't unlock it, just reload checkpoint and keep killing.
As for surviving on harder difficulties, you'll really want to target the enemies holding RPG-7's because they'll inflict heavy damage onto the tank and might cause a game over if War Pig is destroyed. Push into enemy territory if necessary and try to wipe everyone out until Vasquez and War Pig call in for air support. The final checkpoint on this mission is around when you are called back to regroup at War Pig after the two helicopters you called in shoot the hell out of a building.
For completing the mission, you will unlock:
Beating it on "Veteran" will also leave you 50% of the way through earning an achievement later.
MISSION 6: HUNTED
Intel to collect: 2
New weapons off of bodies:
M1014 (Weapon 26)
At the very beginning of the mission, you will enter a shack and see a farmer leave his house where he is approached by soldiers. Wait until Price finishes saying "...old man", then kill the soldier right in front of the farmer with your M1911 .45 (Weapon 27). This will unlock:
Continue reach a closed cellar on the side of a building, then turn around. A helicopter should start having troops rappel out of it. Follow one rope and kill at least three enemies as the slide down that single rope. If you fail, reload checkpoint. Once you pull it off, you will unlock:
Now continue through the entire building. Enter the next building through a door next to a garbage fire, then turn right. On a table with a bunch of playing cards strewn about, you will find intel 10/30. Once you leave this building and continue, you will hear barking. This will be the first section where you can earn the achievement to kill 20 dogs using a quick-time event type thing. (If you are having issues with your allies killing the dogs, then just wait until later in the walkthrough for the second section.) Allow the attack dogs to hit you enough times that it starts an animation. If you press the knife button, , at the right time, you should stab the dog and push him off of you. (If you fail, it's an insta-kill.) This will unlock you:
You may be able to get multiple dogs per run through, but now you need what you did above twenty times. Just reload the checkpoint repeatedly until you have twenty animation kills. This will unlock:
Later in the mission, you will run through a greenhouse and there will be a decrepit building on your left. Jump through the window and walk through to the other side. To your left after exiting the door will be some barrels next to a table. On that table is intel 11/30.
All that is left in the mission is to clear out this area and enter the barn (clearing it out too). You will be tasked with using the FIM-92 Stinger (Weapon 28) to take out the helicopter. It is a lock-on missile launcher. After this you will run down into the next area and hear about an AC-130 entering your airspace. You should see a checkpoint at the top left of your screen, your glitch checkpoint.
Beating it on "Veteran" will also leave you 50% of the way through earning an achievement later.
MISSION 7: DEATH FROM ABOVE
Intel to collect: 0
This mission is pretty straight forward. You play as an AC-130 providing fire support for your allies (including Soap) from the last mission. Actually play through it on Veteran, because from what I've seen, it doesn't affect anything.
Anytime you see a group of at least five enemies, fire your 105 mm gun at it. This includes the straight lines of enemies that run out of buildings. If you can kill at least five with one shot, you will unlock:
For completing the mission, you will unlock:
For beating Hunted and Death From Above on "Veteran", you will unlock:
MISSION 8: WAR PIG
Intel to collect: 3
New weapons off of bodies:
M16A4 (Weapon 29) - Your allies will occasionally drop this
Immediately upon spawning, move to the end of the car and pick up the M249 SAW (Weapon 30) to get a kill with. Quickly proceed to the right of the trash pile and get behind the bus full of enemies. There will be multiple RPGs lying against it. Pick up one and use it to shoot down one of the two helicopters that are dropping off troops. This will unlock:
More soldiers will attack you from further up the road, and you'll want to be very careful not to take cover behind a car for too long lest it explode with you behind it. Now proceed slightly until you hear War Pig say "Gunner! Two-story building at 1 o'clock, second floor!" It will blow a hole in the side of a building on the right side of the road where a door used to be. Enter this hole, then proceed up the stairs to the right. Walk through the door that comes up on your left, and you will see intel 12/30 on a dresser in front of you. Look out of the hole in the wall to the buildings across the street. You should see a weird, red telephone thing. Enter into the building to the right of it, then make the first left inside to go up some stairs. Enter the second room on your right upstairs and you will find intel 13/30 on top of a bed.
It'll be the same routine all the way up this road. Despite initial impressions, no place on the road spawns enemies infinitely; they just spawn a lot of them. Focus on the enemy at nearly all times and only rush towards them if you think you're getting close to clearing out a spot they're appearing in. You'll eventually be fired upon by two machine guns on the second floor of a building in the distance, and once things have been cleaned up a bit, you and others will bust in to the second floor. This will be where the mounted gunners were. Turn left once you enter the room and you will see intel 14/30.
After this, you will just sit around as an enemy tank is destroyed by War Pig and War Pig will proceed towards your building. You should receive a checkpoint around here. Once you do, proceed to do the glitch. For completing The Bog and War Pig on "Veteran", you will unlock:
MISSION 9: SHOCK AND AWE
Intel to collect: 2
Now that Al-Asad has finally been pinpointed, a massive set of Marines have been sent in to the capital to take care of him. You'll start out in a chopper manning a rather heavy weapon, the Mark 19 grenade launcher; fire at the enemy below to make the ground assault go by more smoothly, and make sure you watch the meter on the right side of your screen to prevent overheating. Keep an eye out for tanks as well as heavy fortifications among the rooftops. On Veteran, you'll notice that this section is very trial-and-error, and you'll only know what you're missing when you die. At some point not too far after landing the helicopter, you will go up some stairs where you'll come across allied soldiers. Turn right at the top of the stairs and you should find intel 15/30 lying in the corner. Getting this should unlock:
Now, drop out of the building and follow the fence into a new two story building full of enemies. Proceed upstairs, then follow the wall to the right into the small closet. There, you will find intel 16/30.
As soon as you land, you'll have 90 seconds (regardless of difficulty) to reach the pilot. Just make a mad dash for her and only stop to shoot people directly in front of you. She proves to be a great bullet vest once she's on your back, so you shouldn't have too much trouble returning to the chopper with her. The choppers will take off once she's aboard. As soon as you enter, you should get a checkpoint. Here's where you do the glitch. Once you beat it on "Veteran", you will unlock:
MISSION 10: SAFEHOUSE
Intel to collect: 2
New weapons off of bodies:
G36C (Weapon 31)
As you walk up the hill at the beginning, you should see a big a satellite in front of the first building to your right. Enter this building and clear it out. Now head upstairs and you will find intel 17/30 on a dresser (there are two rooms with a dresser, so look in the other if you don't see it).
A little bit later, you will enter a diner to clear it out. Once you kill everyone, look on the bottom floor for a table holding an RPD, two Mini-Uzis, and intel 18/30.
Now, you must clear out every building for the ending to happen. You're given at most two target buildings to call airstrikes on at a time. Whenever you're able to call in another strike, find the building and call it in until all the buildings have been cleared out, as well as a tank. The tank will be patrolling a road with one of the target buildings near the top of it, which also has a flooded basement. No matter what, the final building you clear will be where Al-Asad is located. You will get a checkpoint right as Captain Price throws a flashbang through the door that Al-Asad is behind. There will be no more fighting at this point, so you can do the glitch here.
Completing the mission will unlock:
Completing the mission on "Veteran" will unlock:
MISSION 11: ALL GHILLIED UP
Intel to collect: 3
There is also a second way to unlock the '20 dog kills' achievement right at the beginning of this mission. Allow yourself to be detected by the first enemies in the mission, and multiple dogs will come after you. You can use these dogs and reload checkpoint until you unlock:
There is an achievement for completing this mission without ever being detected, so restart checkpoint if MacMillan ever mentions that you were (or any enemies start firing at you). We will be forced to break cover for another achievement, but you can just reload your checkpoint right after and be fine. Just follow instructions and make sure to reload checkpoint (or die) if necessary. You unlock the following achievement if you never get detected:
Now onward to the actual mission. Near the beginning, you will enter a church. Run to the other side and climb the ladder to the top. Up here, you will find intel 19/30. Reload checkpoint. Now run in and grab the stinger. Head out the other side, run to the gate, and turn around. Get ready to fire at a helicopter by locking on. After shooting at it, it will pop its flairs. Now, run back inside and grab another Stinger. Use it to shoot at the helicopter again and take it out. This can be very, very annoying. Its shots make your screen go crazy, and dogs will be attacking you from behind. Once you manage to shoot again and take it out, you will unlock:
Later in the mission, you will come to an area with a bunch of large shipping containers. MacMillan will say "Stay low, he's mine." This is your cue to head to the right where you will come across multiple enemies including a guy sleeping in a chair. Kill the guy in the chair, and he should drop the P90-SD. Use it to kill one of the other guys for Weapon 32. Then, grab intel 20/30 off of the barrels in the middle. Now reload checkpoint, and follow MacMillan again.
Later in the mission, you will snipe an enemy sniper at the top of a fire escape, then have to climb it. Ignore where MacMillan enters the building and climb all the way to the top. Jump through the window and grab intel 21/30 off of a table to your left.
You can save & quit at any checkpoint after this for the glitch. Even though you never had to do any fighting in this mission, now there isn't even any killing after this (though, if you kill the dog, a wildly entertaining easter egg happens).
For beating the mission on "Veteran", you will be 50% of the way through earning an achievement at the end of the next mission.
I had a ton of issues recording this, so it skips a tiny bit in a few places and loses audio for awhile
MISSION 12: ONE SHOT, ONE KILL
Intel to collect: 2
You begin the mission next to a Barrett .50cal (Weapon 33) which you must press 
on to start. This a sniping section where you must actually account for wind (unless you wait enough). It also involves my favorite achievement in the game which is an easter egg involving something you learned in Call of Duty: Modern Warfare 3. The main villain, Makarov, of the series was actually in a car down by where you are sniping. You must shoot and kill him with the Barrett and also kill Zakhaev to unlock an achievement.
First, you'll need to find Makarov. Straight above where Zakhaev opens the briefcase, you'll see a car. Now, go to the car left of that one and look in the front seat. You should see Makarov. Second, aim back at Zakhaev's head. Third, wait until MacMillan says "It's now or never. Take the shot!" Finally, shoot Zakhaev (there won't be wind) and hurry up and shoot Makarov. Then, the helicopter from earlier will pop in front of you. Shoot the pilot then run and escape the building. You should unlock:
After you escape the building, you will start with an unsilenced M21 (Weapon 34).
Later in the mission, you will carry MacMillan through a building that contains a few dogs and enemies. Once you get out through the other side, turn right and you should see a ladder going up to a fire escape. Set MacMillan down, then climb all the way to the top to find intel 22/30.
Later, you will drop out of a pool area. Head straight between the buildings. After you turn the corner, you will see double doors on the building to your left. Your second intel in this mission will be behind these after enemies spawn. The most consistent way to get these enemies to spawn is to go over by the pool once helicopters start dropping off enemies. If enemies come from between the earlier buildings, then the door will be open. Run over to these doors and grab intel 23/30.Now, all you have to do is stay alive. There are two popular strategies for this if you're actually playing on Veteran.
You should at this point run into the wooden ticket booth shack between the Ferris wheel and the bumper cars, lying prone and facing the doorway at an angle so you cover the floor as widely as possible. MacMillan can't die, so he'll be fine on his own and not only will you be shielded from grenades, you don't have to do nearly as much work. Grenades will occasionally enter the booth (which you can just throw out the door since you'll be angled to cover the entire floor) and barely any soldiers will be facing you long enough in this position for you to bother shooting them with your USP/secondary weapon. If you were to lie down against one of the booth's walls as opposed to diagonally, you'd have to move around in the booth to be able to throw a grenade back, but you wouldn't know you could throw that grenade back since the symbol is no different from a grenade outside of the booth. There are rare instances when flashbangs (which you cannot throw back) will enter the booth, so you'll just have to pray that no enemies shoot you in the time you're stunned. That probably won't happen though.
When your chopper shows up, wait for about five seconds so there are just a tad fewer enemies to deal with before running to MacMillan. Go prone next to him so you can heal up if necessary, then pick him up and go straight for the chopper.
Put all your C4 around the bumper cars in the grass (NOT on the stage) and the western sides of the fences, replace your sniper rifle if you can, and then run east past them and into the first little corner on the left that you get to. Stay standing and watch for enemy soldiers that might appear so you can shoot them. You'll be protected from grenades around the corner here, and you can blow the C4 when the chopper is about to land to pick up MacMillan and bring him to the chopper.
Your final checkpoint will occur kind of randomly during the final defense sequence. I've noticed it happens a lot around the time the helicopters start dropping enemies in. You will actually have to survive on Veteran for awhile though. Once you pull it off, you will unlock:
For beating All Ghillied Up and One Shot One Kill on "Veteran", you will unlock:
MISSION 13: HEAT
Intel to collect: 0
At the beginning of the mission, you will see a church (which is one of the buildings you had to clear out last mission). Enter the building and climb up some stairs and a ladder to the belltower. Pick up an RPG and just start firing all the ammo (keep 3/4 shots for the helicopter achievement later in the mission) down towards the enemies that should be spawning. Once you use all the ammo, you will unlock:
You will eventually be ordered to get on the turret of a crashed helicopter, so jump on it. You will see 5 helicopters coming in towards the battle in the sky above the church. You must shoot down all 5 of them for the first part of an achievement. After you defend this area long enough, you will be ordered to detonate a bunch of C4. After that you will retreat to the barn where most people finish the mission Safehouse. Head through the main gates on your way there and you should see 3 RPGs. Quickly turn around. Now, shoot down all 3 helicopters from left to right. If you miss one, restart checkpoint. If you killed your 8th helicopter overall, you will unlock:
When that's out of the way, run into the barn and grab the FMG-148 Javelin, then use it on the four tanks in the distance. Now things are going to get difficult. Replace your Javelin with whichever other weapon in the barn you prefer to use and call in an airstrike when you can. It appears that the field in front of the barn is too hot to land at after all, and the evac chopper will ask you to go all the way back down the hill instead, at the gas station that Safehouse started out by.
Toss smoke grenades as soon as you can when the timer starts and try to make a mad dash for the little shack in the corner of the field on your left, which should give you a checkpoint. Get to the deep interior of it and call an airstrike on yourself first, then one outside through a little crack to the south. Now it'll be a bit safer to launch another airstrike on the pile of logs (or a busted car) on the road outside. Rush into the closest house as soon as you have enough room to do so, then make your way downhill. You should get a checkpoint on your way down to make things easier. SSgt. Griggs will greet you at the landing zone; it seems he wasn't deployed to the Middle East when the nuke went off.
Your final checkpoint will be as you get on the helicopter at the end of the mission. For beating this mission on "Veteran", you will be 50% of the way to earning an achievement at the end of the next mission.
MISSION 14: THE SINS OF THE FATHER
Intel to collect: 2
You will spawn with the R700 (Weapon 35) so get a kill with it early. Near the beginning of the mission, you will have to clear out a diner. You must hurry inside and grab intel 24/30 off of the middle-left table before the next cutscene begins.
After you you've been chasing Zakhaev's son, you will eventually walk through a small alley way until you reach a destroyed car and a large red container. Follow this to the right and follow the corner. Proceed up the stairs and grab intel 25/30 from inside the room you enter.
For completing the mission, you will unlock:
You will receive your final checkpoint around the time your helicopter says "Target is on the roof, he's all yours" before you corner Zakhaev's son.
For completing Heat and The Sins of the Father on "Veteran", you will unlock:
MISSION 15: ULTIMATUM
Intel to collect: 1
Late in the mission, you will jump over a broken wall and come across a bunch of weapons on some crates. Go into the next open area full of enemies. You should see a large L-shaped building in front of you. Enter this building from the middle door (that has many enemies come out from it), then turn right. You are going to want to reach the corner room of the building (the part where the L's angle is). In the corner of this room, you will find intel 26/30.
Once you meet up with the sniper team after a huge fight and your team begins talking about the missiles being launched, you should have already recently received your final checkpoint.
For beating the mission on "Veteran", you will be 33% of the way to earning another achievement.
MISSION 16: ALL IN
Intel to collect: 2
After you destroy the first armored vehicle, follow the pathway to the right until you see a fence. Look at the building to the right of the fence and you should see an alleyway before it. You'll find intel 27/30 in the back right corner.
Now proceed through the blown open gate and follow the right side. Eventually, you will reach an open hangar. You will find intel 28/30 in the middle of one of the walls.
Your final checkpoint should be right after you blow up the third, and final, armored vehicle.
For beating the mission on "Veteran", you will be 66% of the way to earning that previously mentioned achievement.
MISSION 17: NO FIGHTING IN THE WAR ROOM
Intel to collect: 2
Depending on your difficulty, you'll have between 9-15 minutes to get to the terminal before the nukes land on the US east coast, so you don't have a lot of time to stick around. Near the beginning of the mission, start following the main pathway. It will slightly curve right through a doorway. Shoot at the handful of enemies in this left hall and be careful around the bend to the next one. Get used to hiding behind walls here. Look through the doors on the left and eventually you will see a dead body on the edge of a table. On the other side of that table is intel 29/30. After this hall is a wider room, and past that is a staircase and the first meaningful checkpoint. Having seven-ish minutes left at this point would be ideal (if you're playing on Veteran).
Two enemies will greet you at the start of this new hallway. When they die, move up a little to make a whole bunch more run towards you at the other end. Try to kill them all when this happens to save time and avoid an unnecessary firefight. Curve right as soon as you can and make your way around the hall, fighting any enemies on the right side as you approach the end. Be careful and watch your left side often. At the end of the hall is another empty hall, leading to a doorway. You may or may not get a checkpoint, so try to wipe out everyone behind you to try to get it to trigger.
The next hall is wide and has a set of wooden boxes blocking the way. Take care of the shotgun-wielding enemies by the next doorway and then run up to the boxes to try to get your allies to move up. Heal up and look past these boxes to get rid of everyone behind them easily, then carefully clean one of the halls on the left or right to get ahead.
Outside of this set of halls is launch control. Gaz and his team will have taken over the security booth, so they'll open the doors for you. Quickly clear the room and head down the hall, then plant explosives and breach the launch control room with the other team doing so on the other side. Clear the room as soon as possible, then enter the abort codes.
Walk up the stairs in the middle of the room and follow the path right to get into that room. You will find intel 30/30 on a table (with another dead body on it) in this room.
Grabbing your 30th intel will unlock you:
Your final checkpoint will trigger once you go up an elevator before fighting for some transportation.
For beating Ultimatum, All In, and No Fighting in the War Room on "Veteran", you will unlock:
MISSION 18: GAME OVER
Intel to collect: 0
Not only is Zakhaev getting away, but swarms of his men know exactly where you are. Ride along the truck you're on and shoot at others filled with enemies. Don't forget that you can crouch for cover if necessary. Some enemies will have RPGs, and those should always be a high priority. When a helicopter comes after you, replace your pistol with an RPG-7 and try to shoot it away. It'll eventually fire at the bridge in front of you, causing everyone to crash.
You have to hop up onto a stable part of the bridge. Normally, the first enemy to jump up in front of you will drop the M60E4 (Weapon 36). If he doesn't, reload checkpoint because this is the only M60E4 in the entire campaign. After a few minutes, the loyalists will tell you that they're coming in to support you, but the tanker will soon explode.
The final checkpoint is received right before Captain Price slides the pistol over to you on the bridge.
For completing the mission on "Veteran", you will unlock:
For beating the game, you will unlock:
For completing the game on "Veteran", you will unlock:
MISSION 19: MILE HIGH CLUB
Intel to collect: 0
New Weapons off of dead bodies:
P90 (Weapon 37) - You may have found a normal P90 earlier, but I considered it more efficient to just grab it here.
The only "Veteran" thing left to do is to complete Mile High Club.Your final checkpoint is right around the time you shoot the enemy that is holding a hostage. All you will have to do on Veteran is to shoot that guy, then jump out the plane.
For actually finishing on Veteran without glitching the checkpoint, ignore the guy in the bathroom on the left and aim down the hall at the soldier standing up. Toss a flashbang into the next room and look away so you're not blinded, then kill whoever's in your way and crouch behind a chair in the next room to reload as the hull is breached. Chuck another flashbang past the breach and face right when you can to find a hidden soldier, who you should kill before he kills you. More enemies will come from the stairs; try to shoot them before they can get to the floor you're on.
Go up one flight of stairs and reload as you do so, then take the eastern staircase and throw a flashbang up there (the goal is to toss it into the next room. Quickly take down everyone in the room and grab the flashbangs on the table here, then chuck a flashbang or two down the hall and shoot past everyone in your way, ignoring the rest. Getting to the hostage is first priority.
You need to shoot the soldier behind the hostage with your pistol while everything is in slow motion, and you only have five seconds (not in real-time) to do so. For a guaranteed opening, wait until there's one second on the clock. After this, just jump out of the plane when your allies break the door open.
For completing the mission on "Veteran", you will unlock:
Some Quick Cleanup
Launch up the mission Crew Expendable on Recruit difficulty. Now, you simply need to complete the mission by only knifing. Just make sure to take cover when you need to and have fun. Also, NEVER reload a weapon no matter what.
Upon completion, you will unlock:
and
Congrats! You're 1000 GS richer!