Black Mesa Incident

The Black Mesa Incident is the basis of Half-Life, its expansions Opposing Force and Blue Shift, and its remake Black Mesa. It was fought from May 17-18, 200X at the Black Mesa Research Facility, in the remote deserts of New Mexico.

It was a five-way one-battle war fought between:
 * The security personnel of Black Mesa, rallied by scientist Gordon Freeman
 * The Hazardous Environment Combat Unit (HECU), a United States Marine Corps special forces unit, rallied by Corporal Adrian Shepherd
 * The Black Ops, a commando unit of US government assassins
 * Xen forces, a race of alien monsters from the alien dimension Xen controlled by the Nihilanth
 * and Race X, another race of alien monsters.