Army of Two: The 40th Day

You will unlock this achievement once you complete the 5th mission.

Once you start this mission your going to be hit with a Flamethrower Super-Heavy, Shotgun Heavy, and a bunch of other light and medium armored enemies. Hide behind the bins and be smart. You may want to drop back to the starting area to take these guys out.

After taking out the APC gunner you will advance to the ladder to get to the balcony. Proceed to the next area.

You're going to face a few rocket soldiers and lots of enemies in the alleyway. You can split if you are playing with another person by boosting him over the fence line to get on the gunner. This will help out.

Once you take out all the enemies you will spawn a super-heavy mini gun once you pass the dumpster. Once you spawn him back track some to take him out. Get your parent on the gunner and you shot out his backpacks with a good scoped weapon that is silenced.

The next part will have a hostage in case you want to save him, so be prepared. This is the last one in the game.

Now you're going to be attacked by a heavy shotgun down the middle after the hostage and plenty of bad guys to take down. Proceed until you start the next area and are captured. Proceed until you meet back up with your teammate.

Once you get to the satellite area make sure you shoot the Neko cat which is setting on top of the satellite, you can't miss him.

Now you are going to have to lift these heavy bombs and place them on the marked areas. You can do this two ways, if you are playing with another person you can have someone carry and someone defend the person carrying. If not I would suggest going out, taking out the baddies and then going back for the bombs to place them.

After the bombs are done your going to be hit with a few more enemies, a heavy, and a moral choice.

You are done, congrats!

All you have to do is complete Mission 5 on any difficulty.
If you are going through this on contractor difficulty use cover and know when to move forward and when you should hold an area for a second.. by the time you get to Mission 5 you should have enough experience in Army of two that you know when and what to do next... if your playing solo guide wisely and play smart, you will come out on top..

i hope i could help!!!!!