Do this on the mission S.O.G! You will get a chance to get the achievement at the end of the mission. You are told to ride the back of a jeep with Woods and the CIA guy (Hicks?). When driving around you have to kill some enemies until tanks come, which you will have the ability to use the missile launcher. Make sure to have a good aim at the tanks and shoot your missiles at them, which you'll be able to guide them. Only use one missile for each tank. There's three waves that consist of 1, 2, then 3 tanks. If you make a mistake, you can kill yourself with the missile or save and quit. If done right, the achievement pops after getting off the vehicle!!!