No human units (infantry, drivers etc.) may mean this is a German game - violence against human/living beings is often removed by developers to avoid censorship.
I've noticed that you haven't specified if the game was real-time or turn-based, but since you mention a grid it's probably the latter.
Your description reminded me of the German
Battle Isle series but that games take place on another planet, although there are both modern day type combat vehicles (tanks, helicopters) and robots
in lieu of infantry.