A bunker is a fortification offering all-around cover, typically constructed to stop small arms fire and most artillery. There were two main functions for bunkers: as direct-fire fighting positions, and as refuges against artillery fire. Bunkers of the latter sort are unfortunately not represented in any CMBO game.

In CMBN, fighting bunkers are available in two flavors: wooden, and reinforced concrete. Bunkers provide excellent cover against both direct and indirect fire. Some heavy weapons such as machineguns may be deployed within a bunker, and infantry units may enter and exit freely.

When purchasing bunkers, players have the choice between unarmed shelters, or bunkers that have a built-in M34 or M42 heavy machinegun. Most bunkers also provide an ammunition cache that can be used by infantry units to acquire extra ammunition.