After many tries, I finally got this one. You can get 8 vehicles pretty easily if you recon and strafe the hell out of all the infantry at the Repair Point before you move in, which prevents them from manning all the tanks. The last 2 are hard tho. I thought I had failed, was stuck on 9, then scoured the map and found one M3 that had been abandoned in a desolate corner (I must have killed it without noticing). Joy!