In areas that they have heavily fortified, they make use of Laser Tripmines, Sentry Guns, and a variety of manned turrets and weapon emplacements. They can also kick their opponents in close combat. In the PlayStation 2 port of Half-Life, they can send grenades back at enemies either by picking them up and throwing them or kicking them. They work in squads and keep in communication by way of radios. They carry grenades to flush out their targets. They wear urban camouflage battle dress uniforms and a Powered Combat Vest, and are armed with grenade launcher-equipped Submachine Guns, Shotguns, M249s, M-40A1 Sniper Rifles, 9mm Pistols and Desert Eagles. They are initially described as working in cooperation with the Black Mesa Security Force in case of emergency circumstances, a role that changes during the progression of their mission. Apart from combat roles, they make take on specialized capacities such as becoming Medics or Engineers.

They are specially trained at the Santego Military Base to deal with a variety of indoor combat situations, particularly those involving dangerous environments and unconventional hostiles. The HECU Marines are sent in to clean up the Black Mesa Research Facility following the incident, their mission being to eliminate anyone with knowledge of the research project and the extraterrestrial life involved.

Black mesa source hecu