Besides gravity and environmental hazards, there are three groups of enemies hunting you down as you travel Medici.
The Military
These guys have strength in numbers, attack vehicles, and weapons to hunt you with. They are normally found around bases and outposts, but are known to run checkpoints along the road in oppressed provinces.
The DRM
The DRM is the local police force commonly found in towns. They lack the weaponry and vehicles of their military brothers, making towns much easier to take over. However, raise your heat too high and the military will still show up for the fight!
The Black Hand
These guys are the cream of the crop, providing the greatest challenge in defeating them. Use heavy weapons, environmental items, grenades, vehicles, and anything else you can throw at them.