Get Off the Ground Achievement
Get Off the Ground10
Kill everyone in the convoy from ground level, except for KreidlDuring Mission 1, 'Schoneberg Convoy', you will come to a street where you will need to stop a convoy by shooting the explosives you've planted (shooting the explosives and destroying the leading armored car will not void this achievement). By doing this, you should unlock Novice Sniper (10G) if you haven’t done so already.
After shooting the explosives, Dr. Kreidl will exit a transport truck (the objective marker will be on him). At this point, shoot Kreidl ONLY; do NOT shoot any other enemy. After sniping him, follow the objective markers down to the street, and instead of recovering his documents, begin to take out the remaining enemies from the ground. After about 4-5 kills, there will be a short cutscene where a tank will show up. For the time being, ignore it and continue eliminating everyone until the achievement unlocks.
Note: More troops will show up when the tank does, but it is not required to kill them for this achievement. Stick to the street where the convoy has been stopped (around the corner from the tank) and just kill everyone you see.
Thanks to 360GameTV for the video: