The Red Solstice 2: Survivors - M.E.R.C.S.

When the colony of Tharsis was declared unsalvageable, the corporations pulled out — but the M.E.R.C.S. stayed until the absolute last minute, getting civilians out before SOLAR came down. The survivors who made it abandoned any loyalty to the corporations and folded into the small M.E.R.C.S. faction, heading out into the Martian wasteland with nothing but each other. The rules that apply now are the rules of the road.