When I approached the truck he spotted infantry, told him to open fire. Told my guy to get in as gunner in the off-road and look to the north. Took one guy with me and we moved in to search for the truck. Told my guys to target some more patrols but to hold fire. Silently killing this patrol did not alert any of the other guards. When the two guys moved into the kill zone, and my silenced shooters reported 'ready to fire'), I gave the the 'Fire' command (unlike the 'fire at will' command, the 'fire' order ensures that the AI will hold fire once his assigned target is down). Told the three guys that had silencers to silently target (hold fire then right click on target) the two man patrol on the southern side. Approach the first fuel truck from the SE.
Rendezvous with the first team, crossed the road, rendezvous with the second team. If that's any help to anyone, here's how I did it: I play on vet but maybe I just got lucky. That's odd, I didn't feel this mission was too big of a challenge.
