Operation Flashpoint: Red River

I got this at the begining of Mission 3, When you go into clearing the trading post and the container market.

Now the only way I can see getting this achievement is when your in a built up area, you clear that area without you or your team mates taking any damage.
I was a scout man aswell, using a sniper to pop them off this is how I got it.
Hope this helps

This is obtained when playing Mission 3 - The Human Terrain.

All you have to do is play through the first part of the mission where you have to clear out a couple of villages and then a container yard. Once you have killed all the enemies in the container yard you will get this achievement.

The only way you won't get this is if you are playing co-op and your buddies clear out the area while you are dead. If this happens you will have to re-do the first part of the mission to get the achievement.