|The following is based on Fallout Tactics and some details might contradict canon.|
Vault 0 (zero) is a location in Fallout Tactics.
Constructed in Colorado, this installation was designed to be the nucleus of the entie Vault network. Protecting the greatest minds of the time, it was supposed to spearhead the post-War civilization of America. It would do so by executing the Exodus Protocol: reuniting the Vaults and then using Vault 0's sizeable stocks of advanced machinery to tame the devastated land when outside temperature, radiation levels, and poison particle counts return to acceptable levels. 
To coordinate the effort and control the functioning of the Vault, the Calculator was created, an advanced supercomputer using an electro-organic terminal to link its central processing unit to brain stored in pseudo-cryonic conditions, fed specifically formulated nutrients to sustain suspended life. This scheme was intended to assist the Calculator in Vault management, including life support, food production and distribution, pacification robot protocol, and Vault-0 defenses. Ultimately, it would also aid in executing the aforementioned Exodus Protocol.
However, these lofty goals were compromised. Before the war happened, the Committee responsible for managing the construction of Vault 0 introduced budget cuts (by a 30-3 majority, no less), reducing the sum allocated for computer backup systems from 24 billion dollars to 2.3 billion, to cover pay increases of senior committee members. Additional plans called for a modification of compartments that were designated for backup computer and life support systems into senior vault personnel leisure facilities, including several top quality restaurants with 10,000 square feet of cold storage, seven smoke rooms with piano bars and two subterranean hunting grounds stocked with rare animals purchased from world renowned zoos. The renovation had a projected cost of 12.4 billion dollars. All due to a “dwindling” chance of nuclear war ever taking place.
On October 23rd, 2077, history proved them wrong. As the nuclear devastation reduced the United States of America to ash, the Calculator ended up in what can be best called a slumber. It did not react to the nuclear holocaust, instead silently remaining hidden beneath Mount Cheyenne, along with its robotic servants and pre-War charges slumbering in cryonic suspension. It slept for over a century.
It all changed in 2196, when a group of supermutants from Gammorin's forces breached Vault 0's perimeter. This action activated the Emergency Pacification Protocol, designed as contingency in the event of substantial foreign military presence on US soil, dangerous mutations or breach in the Vault's defenses. The Calculator promptly introduced the invaders to a Behemoth and began executing routines included in the protocol. The awakening of the Calculator also exposed the blunders made by the Committee overseeing its construction. The lack of backup computer systems impaired its functioning and damaged the electro-organic linking terminal. The results? Sixty three percent of Vault 0's population dead, with a further fifteen percent suffering from severe brain damage, to the point of being unable to care for themselves. Among the dead were First Scientist Napstarsky and Second Scientist Jones, the only people able to repair the damage. Constrained by its inflexible programming and lack of actual intelligence, the Calculator coldly executes the Pacification Protocol, expanding its operations into the Buena Vista nuclear reactor complex and industrial facilities in Canyon City and Great Bend to augment the Vault's own production capabilities.
Thus begins a campaign of extermination against the wasteland and its inhabitants, stopped only when the Warrior penetrates the Vault and deals with the emotionless machine.
Vault 0 thus becomes the end-setting of Fallout Tactics, as the player character, the Warrior, and their team of Brotherhood of Steel Paladins have to stop the machine. The Warrior's squad comes to Vault 0 after triggering the nuclear explosion that opens the Vault door.
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The mission in Vault 0 is to activate three power nodes throughout the vault in order to reach the Calculator. The players finally met the famous Dagger Squad of the Brotherhood, which consists of squad leader Paladin Lord Maximus, Tais, Maelyra, Khronis, and Phoenix.
Dagger Squad aids the Warrior in defeating the first wave of Vault protectors, and then secures the lift which is used to enter the Calculator's chamber. However, the Vault power nodes were rendered offline after explosion, so the Warrior has to activate them.
Going through security, living and cryonics sections of the Vault, the Warrior battles many robots and encounters remnants of Vault 0's citizens, who were revealed to be severely brain-damaged due to malfunctions in the cryonic chambers. Ultimately, the Warrior activates the power nodes and proceeds to the lift, entering the Calculator's main lair.
- The concept of Vault 0 is often considered inconsistent with the Vault Experiment from the other Fallouts',
- The technology, aesthetic, and design of Vault 0 has nothing in common with other Vaults.
- The game makes the common mistake of confusing cryonics with cryogenics. Cryogenics is the study of generating very low temperatures; the science of preserving humans and other organisms in these temperatures is called cryonics (without the -ge-).
- The door is opened by a point-blank detonation of a nuclear warhead. This does not mean it is weaker than e.g. Vault 87's door, as the latter's was rendered inoperable by a surface detonation of a warhead above its entrance cave.
Vault 0 appears only in Fallout Tactics.
 See also
 Developers quotes
Vault 0 is designed to repopulate the continent if the other vaults fail. It contains the biggest "brains" of the time, and their genetic data.”— Ed Orman
The sturdy Vault 0 was to be the nucleus of the vault network. Housing the greatest leaders, artists and scientists, the inhabitants of Vault 0 were to reunite the vaults and lead the people to a new life, a new world. But, after the bombs, the world would be a harsh one. To ensure the creation of a post-nuclear utopia, the Vault Dwellers would need help. Machinery was constructed to tame a land hardened by the ravages of war, then tempered by nuclear winter.”— Gareth Davies
 Behind the scenes
- Cheyenne Mountain remains a military base today and is located in Colorado Springs, Colorado. It is the location of most of the United States' missile targeting systems and missile defense systems.
- The Cheyenne Mountain Complex is also the location of the fictional Military Strategic Defense Initiative, like the Sentient Computer System called "SkyNET" from the Terminator series of films. Many further Terminator references are made throughout the Fallout: Tactics. It should be noted that in contrast with SkyNET, the Calculator is not sentient or even an AI - it's simply a computer following pre-programmed routines, cut off from the actual intelligence that would control it.
- The Complex was also used in the television series Stargate SG-1 as the base of operations for the fictional "Stargate" program.
- This is also the housing for the fictional W.O.P.R. super computer in the movie War Games.
- ↑ Intro: „The sturdy Vault Zero was to be the nucleus of the vault network housing the greatest leaders, artists and scientists. The inhabitants of Vault Zero were to reunite the vaults and lead the people to a new life, a new world. But after the bombs, the world would be a harsh one. To ensure the creation of a post-nuclear utopia, the vault dwellers would need help. Machinery was constructed to tame a land hardened by the ravages of war, then tempered by nuclear winter. But plans were barely in place when the first missiles left the silos. During the destruction, communication between the vaults ceased. Entire vaults were lost; those that survived were on their own.”
- ↑ Chapter 1 cinematic: „With your initiation now over the Brotherhood now reveals to you their highest objective, fragments of data, left over from before the great war show that the ancients spent many years constructing Vaults to house the survivors. Recently acquired data however points to the creation of an enormous super Vault; this nucleus of the vault network was built to protect the greatest minds of the time and would be the spearhead of post war civilisation. If the Brotherhood could find this vault and activate its systems, they would have access to technology resources previously undreamed of. As well as access to the ancients themselves but the journey to the calculated location of Vault 0 would be perilous. A large army and a vast area of operations would be required for a mission of this magnitude. „
- ↑ Chapter 5 cinematic: „In the paranoid times leading up to the war, new Vaults were being constructed every day. The ancient's temples of war known as NORAD became the home for Vault 0, a storage place for the cryogenically frozen geniuses of the time. The Calculator was built to be a mixture of machine and man, a gestalt of mechanical switches and human brains linked through a cybernetic interface. Supposedly representing the ideal society, these brains were to govern the higher functions of the Calculator, powering its neural network. The Calculator was designed to oversee the repopulation of the continent in the event of a war and educate the new humanity in the ways of the old world but first it was to sterilise the land making a fresh start for the soon to be emerging citizens of Neo-America.”
- ↑ Canyon City terminal: „...good question, Dr. Jones. I would be happy to explain why we're taking "the path less traveled" when compared to mundane computer systems. One advantage the Calculator has over normal computers is the electro-organic linking terminal. Our tests conclude that the CPU can share tasks and receive data from pseudo cryogenic stored brains that are maintained in an oxygenated tank. These brains are currently that of lab rodents, but our calculations indicate that human brains can be preserved in the same fashion. The brains will be fed specifically formulated nutrients to sustain suspended life. In turn, they will assist the Calculator's CPU in Vault management, including life support, food production and distribution, Pacification-Robot protocol, and Vault-0 defenses. This neural network will also assist in Vault-0's primary function: To initiate Mankind's post-war rebirth. When outside temperature, radiation levels, and poison particle counts return to acceptable levels, Vault-0 will remotely activate the Exodus Protocol, which will initialize the integration of all Vault Dwellers onto the planet's surface. The brains are to be harvested from a select group of geniuses that were chosen, by committee, for their skills and their cute haircuts... (fade to static).”
- ↑ Canyon City terminals: „Committee rules 30 to 3 in favor of streamlining Vault-0's computer backup system costs from 24 billion dollars to 2.3 billion. These cuts will take place immediately. This ruling was based on the dwindling chance for actual nuclear war taking place along with much needed pay increases to senior committee members. Furthermore, the subterranean Vault compartments that were designated for backup computer and life support systems will now be renovated for senior vault personnel leisure facilities. The committee has a construction agenda that must be finalized by mid March. The new facility options are as follows; several top quality restaurants with 10,000 square feet of cold storage, seven smoke rooms with piano bars and two subterranean hunting grounds stocked with rare animals purchased from world renowned zoos. All of these are feasible but require an additional 12.4 billion dollars which can be acquired by... *click*”
- ↑ Latham's journal: "Journal of Sir Latham, Entry 1.4.5. Today is a day filled with absolute horror.\n\n Only one mutant returned from a scouting trip that was ten soldiers strong. He staggered back to camp and collapsed without a sound. He died in my arms while trying to hold back the blood pouring from his mouth. Before I had a chance to close his eyes, the menace was upon us! Metallic death machines entered the camp undetected by my sentries! I have never seen creatures such as this before, but they seemed unstoppable. It was only the sheer power and, more importantly, our numbers that allowed us to defeat these three machinations of death. Our losses were staggering." Note: The date format is y/m/d, basing on other entries.
- ↑ Buena Vista: ”...our lands are filled with foreign soldiers, dangerous mutations or breach of the Vault's defenses, the Calculator will initiate the Emergency Pacification Protocol. This will trigger the starting sequence for the Pacification Systems and the operations...
- click* *zzzt*
- click* *zzzt*\n\n\n
- ↑ Vault 0: “(Static fading) ...is Third Scientist Lewis with the report on the cause for the perimeter alarm.\n\n Late last night, a heavily armed group of mutated humans attempted to force their way into the vault. I have never seen such creatures. The smallest one was over seven feet tall and must have weighed at least four hundred pounds!\n\n I believe that this group has seen fighting recently. Each one was carrying enough firepower to arm a small platoon, but the real shock came when a security camera was able to get a close up.\n\n These poor creatures are severely mutated with the majority of their features only vaguely resembling that of human beings. I don't know if they are a product of nuclear radiation - they seem to share too many similarities with their muscle bound frames to credit a random mutation.\n\n Their intrusion in the Vault has fully woken up the Calculator and the Emergency Pacification Protocol has been initiated. I don't believe the invading mutants were expecting to combat a Behemoth but the results were... (Fade to static).”
- ↑ Vault 0: “(Static fades out) ...is Third Scientist Lewis. Things are going from bad to worse. We should have installed more backup systems for the Calculator. The irony is that the committee members that voted on Vault 0's backup system budget cuts are now all dead, but it gets worse. Sixty three percent of Vault 0's population is now dead, while fifteen percent of the living are now severely brain damaged and can no longer care for themselves. My frustration builds with the fact that I can't even get into the Calculator's chamber anymore, due to lack of authorization! If only First Scientist Napstarsky or Second Scientist Jones had survived instead of me. They might have been able to repair the electro-organic linking terminal, and who knows, they even might have saved Vault 0. I will do what I can, but... (Fades to static).”