This will come early on and the mission is split into 3 waves. You will have air support to help.
First wave is artillery and is way to deal with even though there is quite a few.
Second wave is 4 tanks that will need to be dealt with quickly as your ground troops will die quickly. Use your AT-2 rockets and these will be destroyed quick.
Third wave is more tanks, but they are off in the distance and can be destroyed with your AT-2 rockets again. Once this wave is completed, you will unlock your achievement.