How do I use ammo trucks?

[Imp]

Ages ago I had a real tough battle for both sides, he had managed to reload his TOS-1s But I was after them & he was having to use them in direct fire mode vs my tanks. There were lots of little clumps of close cover & on his turn 3 ammo trucks charged my armour. Stopped 2 at a couple of hexes which if I remember both blew up the third got right up to a tank but luckily did not go bang when it died.
It was a totaly crazy battle you would load the game & see a tank company had vanished before even hitting the replay button.