Operation Flashpoint: Red River

ok if your'e going for this you must be familia with the controls (play some missions first) and have a full team with mics.

you have 10shared lives at the start, 1player must be alive in order to respawn, only people alive and in the chopper will get this, it works if you join a game in progress, chopper wont take off if some people are in it and some arnt even if there incapped so while its waiting you are vulnerable.

start a game up on last stand and choose the first map.

1rifleman with M4+scope, secondary M16+scope
1grenadier with M4+scope, secondary doesnt matter
1scout with any sniper, seconday should be an assault rifle preferably the m4
1gunner machine gun, secondary doesnt matter

now this isnt going to be easy. on the map when you land follow the way points till your at the top of the hill, the grenadier n machine gunner should loose there 2ndaries 1get the sam launcher, 1 the SMAW both are located inside the building next to all the ammo (look for the main area objective sign)

waves 1-1 to 2-4 are easy so i wont go into detail, just be sure get all bonus objectives as they give you fire support, dont use them.

at the start of 3-1 the leader should run the extraction to get the chopper to land. leave it there. as your looking down the road on thehill facing area 1+2 have the sniper on a roof to the left (as you look down) of the road, the machine gunner behind the rocks infront of it, the rifleman at the sandbags and the grenadier with the sniper.

this should give you cover from the front and all the left flank, rifleman note there is a fixed gun next to the sandbags near the chopper. you should have a good defense from most of the ground troops jeeps and apc's. tanks show up around 4-2.
call in 1 support (mortor/jdam/missle strike) at the start of each wave in 4 after the sniper sees them at the bottom. best to put it at the main road. 4-4 is hard, solid infact work together and get them to fall back ass soon as they do all throw smoke in the choppers direction and run to it, dont board untill you see it say 5-1 as if anyone gets in it sooner wont get this achievement

The difficulty of this achievement depends a lot on how many humans you're playing with. If you've got 3 or 4, then with the right strategy this is very doable. If possible, I highly recommend you go for this at the same time as With A Little Help (play with three friends). If you have fewer than three humans, you can still use this guide as a rough strategy, but it'll depend much more on shooting skill and your ability to adapt.

You don't actually need to worry too much about your loadout, or making sure you have a wide distribution of classes. It's best if everyone is Grenadier, ideally with the anti-tank mines if you're leveled up enough, and the starting Specialization (which gives better armor or health). For your core skills, priority should go to the reload/weapon switch. Again, it doesn't matter too much--when I got this achievement, two of my partners had never played further than the first mission.

Play on the first Last Stand mission, Contested Front. Everybody should stay on the main hill at all times. Three players (or two, if you brought along an AI) will stand on the roof of the L-shaped building in the middle south of the hill. It has a stinger leaning against the side of the stairs, at ground level. These three players will be using the SMAW. Face north from the building, and there should be a building across the street you can enter. Pass through, cross the street, and there will be a SMAW reload point across another street. The trip is pretty quick and easy. You'll get five rockets at a time. You three will do the bulk of the killing, and you'll be doing almost all of it with those rockets. Prioritize enemy (land) vehicles. If you see enemy infantry running around, blow them up--you don't have a good scope and you're not very accurate, but that doesn't matter when you get to make a big explosion.

The fourth person is on anti-air duty. You should move to the southeast building of the main area. The right building is again L-shaped, and part of the roof is covered and contains a stinger reload. Any time you hear anything about targets of opportunity (the bonus helicopters that give you support missions), special forces (who arrive in a vulnerable chopper, flanking the main area), or attack choppers, be on the lookout and take it down. Your second priority, when there aren't any helos to worry about, is using your rifle. If enemy infantry is flanking the area, you should take them out. If you notice infantry getting up the hill and too close to your teammates to the west, take them out.

And that's really all there is to the strategy. If you do that, there will be hectic moments toward the end but for the most part it'll be much easier than trying to rely on rifles. My group was able to do it with two pretty inexperienced players, and I'm not all that great at shooters myself. The worst trouble we had were from the attack helicopters. There are a few other tips that are less important, but might help out.

-Keep an eye on the map (the back button ). Since reloading the SMAW takes a few seconds, I'd typically glance at it during a reload. It can help you figure out where enemies are--and if they're flanking you--even if you don't actually see them yourself.

-Communicate! Our stinger player especially was a huge asset, letting the rest of the group know where enemies are. Even for the SMAW players, the time it takes to reload or run for more ammo is time your teammates can be killing if you spot an enemy and let them know where.

-Enemies WILL come around the back of the base. If your grenadiers are leveled up enough for anti-tank mines, a few placed on the rear roads will help cut back on surprise tanks. Either way, it's something to be careful about.

-If enemies DO come into the base, let the group know, but make sure not everyone runs after them. At least one of the SMAW group should remain up front.

-Support missions aren't totally necessary. I didn't even bother using mine until wave 4-4. But--they are still useful, and unloading them all in 4-3 and 4-4 will help you cut the hardest waves short.

-Don't bother calling in your transport helicopter early. If enemies get too close to your base, it'll take off. If it does take off, you have to wait a bit to summon it again. We didn't summon it until the enemies from 4-4 were already falling back, and enemies from wave 5-1 had started approaching the base by the time it landed and we could hop in. We were reasonably safe, but calling it earlier would've given us a little more of a buffer and that much more safety. I think the best time to call it would be when the game lets you know you're almost--but not entirely--done with 4-4.

-And speaking of the transport helicopter, make sure you see 5-1 appear on screen. If it still says 4-4, you probably won't get the achievement even if you've gotten the "they're falling back!" message.

-Plan for this to take somewhere between an hour and a an hour and a half.

This is an old and inactive game, but I hope this guide helps someone! If you have any issues with this guide, please let me know. I'm happy to incorporate suggestions.