Black Mesa Incident

The Black Mesa Incident was a catastrophic event resulting from an experiment carried out at the Black Mesa Research Facility. Its aftermath would see the invasion of multiple races of extra-terrestrials into Black Mesa; a resulting battle between human military forces and Xenians which would conclude in the complete destruction of the facility and almost all of its inhabitants; and, in the long term, attract the attention of the Combine Empire to Earth.

Cause
The Black Mesa Incident was caused directly by an experiment in Sector C Test Labs' C/33a Test Chamber. The experiment was supposed to analyze an extremely pure sample of Xen crystals, which various expedition teams had been collecting from the borderworld.

The GG-3883 sample was, in addition to being the purest, also the most unstable Sector C staff had experimented on. With the Administrator of Black Mesa keen to see positive results from the test, the Sector C staff decided to boost the anti-mass spectrometer to 105% power, much higher than the equipment's safety buffer zone of below 90%, in a bid to garner better data. Eli Vance, one of the research leaders, argued against this decision but was overruled.

Dr. Gordon Freeman was the scientist responsible for the insertion of the sample into the anti-mass spectrometer for analysis. As Freeman was preparing to do so, one of the overseeing scientists noticed a small discrepancy in the readings, but dismissed it as "within acceptable parameters". Upon receiving the sample, Freeman proceeded as ordered and inserted the sample. As the sample touched the machine's beam, a catastrophic resonance cascade began.

Immediate Effects
The cascade had far reaching consequences. An expanding dimensional rift was brought into being, which caused extensive damage to the facility and summoned swarms of aliens to Black Mesa, teleported from the borderworld the crystals originated from. Thrust into an alien environment, these creatures were highly aggressive and attacked the Black Mesa personnel on sight, which resulted in heavy casualties among science and security personnel. Although the appearance and behaviour of these aliens seemed and was to a certain extent random, it swiftly became apparent that certain of the creatures were acting as one, less like confused animals and more like a determined military force, looking to establish a hold over their new environment.

Three survivors of the initial disaster, Dr. Gina Cross, Dr. Colette Green and Dr. Rosenburg, made their way to the surface and called in the military to help them with the alien onslaught. The military, in the form of the Hazardous Environment Combat Unit arrived quickly, bringing in troops, ordnance and vehicles via aircraft and trains. Aside from dispatching the aliens, these troops were also instructed to permanently silence the facility personnel. The HECU's foray into the facility was initially successful. They managed to establish control of Black Mesa's surface facilities and began to make inroads into its extensive underground, setting up several fortified outposts to keep the aliens at bay. They also managed to capture Dr Rosenburg, who sent the distress signal, and locked him in a cargo car for interrogation.

While HECU established their presence in the underground, Dr. Green and Dr. Cross worked to prepare the satellite delivery rocket for launch, with the aim of reducing the effects of the resonance cascade. However, the launch was aborted when soldiers captured the control room and massacred its personnel, Cross and Green presumed among them.

Barney Calhoun, a low-ranking security guard, managed to survive the initial events. Determined to escape the crumbling facility, he located and freed Dr. Rosenburg. With his aid, Rosenburg located the old, abandoned A-17 Prototype Test Labs used for teleportation experiments. Calhoun helped the doctor by acquiring several key components of the machine, and narrowly escaped with him and his two colleagues, Walter and Simmons, just as the HECU stormed the underground facility.

Escalation
The battle between the HECU troopers and the Xen invasion force escalated as the dimensional rift widened. The soldiers began to be pushed back as more aliens appeared, including the deadly likes of Alien Grunts and Gargantua. Heavy ordnance began to be utilized as the aliens spilled out onto the surface, in the form of upgunned M2 Bradleys, M1 Abrams main battle tanks, mortars, airstrikes and artillery bombardment. The facility turned into a confused and quickly deteriorating warzone. As the battle raged, Gordon Freeman, the scientist responsible for the original incident, became a top-priority target for the HECU, as he consistently avoided capture and overcame the military on many occasions in his attempts to halt the dimensional rift. He successfully launched the satellite delivery rocket prepared by Dr. Gina Cross and Dr. Collette Green. Shortly after this he was captured by HECU troopers. Instead of being taken for interrogation, he was dumped by two marines into a trash compactor. He narrowly escaped death and managed to work his way through residue processing areas before reaching the Lambda Complex, where the remaining members of the science team were holding out.

While Freeman progressed through the surface facilities, the conflict began to favor the Xenians, as heavy Xen weaponry and aircraft began to arrive, shooting down one of the reinforcement fleets carrying Adrian Shephard's squad. HECU soldiers found themselves overwhelmed, and with most of the original strikeforce slain those who remained fell back into the underground or began to evacuate, using airstrikes to cover their retreat. With the failure of the military force, the black operations contingent arrived, who set about killing any remaining human survivors and preparing a high-yield nuclear warhead to obliterate Black Mesa.

Shortly after the evacuation began and the black ops troops arrived in full force, Freeman gained access to the Lambda Core complex. He was informed by one of the surviving scientists that the discovery had been made that the alien forces were being controlled by one super organism. Not only was this creature directing the entire Xenian invasion, it had taken control of the dimensional rift; as long as it remained alive, the invasion would continue and eventually consume the whole of Earth. The ragtag science team resolved to send Freeman to Xen via the Lambda teleporter in order to slay the super organism. The teleporter was destroyed by invading Xen aliens in the process.

Last hours
As the Black Ops assessed the situation via interrogation of captured HECU soldiers, a new and unknown foe appeared, the so-called Race X. One of the survivors of the HECU force, Corporal Adrian Shephard, managed to fight his way through swarms of the deadly aliens in a desperate attempt to find and escape from the infested base. Shephard and a few other surviving soldiers overcame several squads of the Black Ops soldiers, and managed to deactivate their warhead.

Meanwhile, Gordon Freeman confronted the Nihilanth in Xen and succeeded in killing it. This action halted the Xen invasion, allowing the mysterious G-Man and his employers to temporarily take control of the borderworld. The G-Man reactivated the nuclear device, and detained both Gordon Freeman and Adrian Shephard at an unknown location and by unknown means. With the detonation of the warhead and the death of the Nihilanth, the Black Mesa Incident, as well as the facility itself, came to an end.

Aftermath
The consequences of the Black Mesa Incident were massive. The relatively small inter-dimensional rift caused portal storms to open all over the Earth, bringing large amounts of Xen wildlife to the planet and attracting the attention of the Combine Empire, which attacked and conquered Earth following a brief seven hour war. Dr. Wallace Breen, the former administrator of Black Mesa, was able to negotiate a surrender with the Combine on behalf of the human race, and as a result became puppet ruler of Earth. The death of the Nihilanth also ended the slavery of the Vortigaunt race, earning Gordon Freeman their eternal gratitude.

Although the incident is largely considered to have been a terrible accident, there is incidental evidence which suggests it was to some extent engineered. The Nihilanth seemed to have been planning the Xenian invasion for some time, and the G-Man has more than once hinted at his own manipulations of the affair, most notably when he whispered to Eli Vance just before the beginning of the resonance cascade to "prepare for unforeseen consequences". To what extent either of these individuals were involved in the authoring of the incident is not at this time known. Further dialogue at the end of Episode 2, in the chapter; "Our Mutual Friend", suggests that the G-Man played some role in providing the Xen crystals to Black Mesa, and there is mention in the original game that The Administrator (Dr. Breen) went to great lengths to obtain the crystals, although it is unclear if he was aware how they would react during the experiment.

Known Survivors

 * Gordon Freeman
 * The G-Man
 * Barney Calhoun
 * Isaac Kleiner
 * Wallace Breen
 * Eli Vance
 * Alyx Vance
 * Doctor Rosenburg
 * Doctor Richard Keller
 * Walter Bennett
 * Simmons
 * Adrian Shephard
 * Arne Magnusson
 * Unknown number of HECU forces
 * Colette Green?
 * Gina Cross?