One of the few old world organizations to survive the Great War, the Enclave was once the shadow government of the United States. Members of the conspiracy both embraced the idea of a nuclear war and knew that the common man could not survive it. They believed that as long as the "important people" of the United States survived, they could regroup quickly and wipe out communism once and for all. Though not technically part of the Enclave, many powerful corporations benefited from the Enclave's actions and their research facilities were protected during the firestorm of 2077.
In 2073, as the global race to exploit the handful of remaining natural resources reached its fevered peak, the United States managed to stake a claim on the world's last known supply of crude oil, buried thousands of feet beneath the Pacific Ocean. Poseidon Oil, a major U.S. energy concern, was contracted to build an oil rig and extract the oil. Before long, the oil ran dry and it was abandoned by Poseidon. Come 2077, with total nuclear war rapidly arriving at America's doorstep, the President of the United States and a number of other members of the conspiracy left their posts to take refuge on the Poseidon oil rig, this was later mentioned as the worst in American Enclave history do to such catastrophic containment. Here, the President himself set up a secret base from which the USA could continue to exist and wage war on China, with the eventual goal of retaking the continental United States. Some members of the Enclave retreated to remote locations in other parts of the world, but when the bombs hit, they lost all contact with the main group.
The Vault ExperimentEdit
The Vaults were funded by the U.S. government and, accordingly, the government had control over them. Ostensibly, they were intended to allow a selection of privileged United States citizens to survive the Great War. Secretly, however, a large part of the Vault Project had a far more sinister goal.
The U.S. government's real plan to survive a nuclear war was simply to find another planet to live on after blowing up this one. A spacecraft designed to ferry the human race to another planet was either under construction or ready to go before the War. The plan was for the government to flee to the oil rig, and then leave in a spaceship for another planet. 
Any voyage to space or recolonization of Earth would have been very difficult and fraught with unforeseeable complications. Thus, many of the Vaults were designed to have some sort of critical flaw in order to test how an average American would be able to deal with various circumstances. Vault 12 in Bakersfield had a faulty Vault door that wouldn't close all the way, allowing dangerous radiation to leak in, leading to the creation of California's ghoul population. Vault 15 was built normally (the rock slide that buried its control center was accidental), but was populated with a diverse mix of races and people to see what sort of tensions arise when varied backgrounds are packed into a small environment. Vault 13 was intended to stay shut for a full 200 years to test the effects of long term isolation. Vault 101 was to be sealed permanently to study the evolution of small communities in complete isolation from the rest of the world. The types and purposes of the experiments go on.
Eventually, due to either a change of plans by the Enclave's leadership or the spacecraft being destroyed, the Enclave abandoned their initial goal of settling on another planet, and decided to resettle the one they already had, although the Vault monitoring and research continued as the Vault Behavioral Project. In order to monitor the populations being experimented upon, the Enclave's oil rig possessed a great deal of equipment that allowed them to observe and control the Vaults. For example, the Enclave sent the all clear signal to Vault 8 shortly after the War, prompting them to leave their Vault and build their city. These monitoring tools also let the Enclave see that the population of Vault 13 was largely intact, although this wouldn't become important until much later.
Rise to PowerEdit
For a long time after the Great War, the Enclave sat quietly in its oil rig, consolidating its forces and working on gaining a technological edge over anyone on the mainland. Eventually, when they felt it would be safe, they decided it was time to move out and start working towards the rebirth of America. Using their vertibirds, the Enclave sent out scouting parties all over California, the closest state to the oil rig.
The Enclave scouting parties arrived in California after the Master's defeat, and so saw super mutants and ghouls inhabiting the land. When this was reported to the higher ups at the Enclave, it was decided that all the mutants would have to go. It occurred to the Enclave that those who had lived out in the open on the mainland for over a hundred years since the end of the war must have been contaminated or compromised somehow by radiation...or worse. These mutants too, then, would have to be destroyed before "true" humanity (as defined by the Enclave's leadership), could once again lay claim to the mainland.
Reconnaissance and exploration of California continued, looking for a way of carrying out their genocidal ambitions without destroying the world all over again with nuclear weapons. Eventually, Enclave troops stumbled across the old abandoned Mariposa Military Base, where research on the Forced Evolutionary Virus had been done before the Great War. The FEV was what had created the super mutants, the biggest threat of all to the Enclave.
The Enclave excavated the military base, largely using slave labor gathered from the nearby mining town of Redding, eventually finding the vats deep inside the lower levels of the base. Though they had been buried in rock and forgotten for decades, the vats still contained that old familiar green bubbling gunk, the Forced Evolutionary Virus. The Enclave gathered samples to be sent back to the oil rig for further analysis. Before long, though, the slave miners, some being fully exposed to raw FEV, others likely falling into the vats accidentally, began to mutate into a second generation of super mutants. The mutant slaves soon overthrew their guards. Seizing their weapons, hardware left behind by the first mutant army or anything lying around, the super mutants stormed the upper levels and quickly overran the troops in the base. Panicked and retreating, the Enclave troopers on the upper levels fled the base and used explosives to seal the entrance, trapping the second generation mutants inside the base.
Even though things went badly at Mariposa, the Enclave still had the samples of FEV they needed. Back at the oil rig, the United States Chemical Corps began work on the serum immediately. They found that it would be possible to make from FEV an incredibly potent and lethal toxin that only affected mutants. But, in order for research to progress, they would need test subjects. They needed two test groups: one of clean, pure humans and another composed of the "mutants" that lived all over the mainland, suffering radiation and FEV exposure for decades that, to the Enclave, made them unclean. The unclean sample was easily obtained by kidnapping the entire population of Arroyo.
The clean group would be more difficult to obtain though. The Enclave wouldn't allow the Chemical Corps to use people living on the oil rig so they had to look elsewhere. Thus, they traveled in force to Vault 13 and sent a command to the Vault's computers to open the Vault door. After taking care of some mild resistance(after shooting three unarmed vault dwellers who came to greet them), the Enclave troops rounded up the residents of Vault 13 and shipped them off to the oil rig in vertibirds to take part in the Chemical Corps' FEV experiments.
Fall and AftermathEdit
Just as the Enclave was preparing to launch the poison into the jet stream to kill the entire population of the mainland, a tribal known as the Chosen One arrived at the oil rig on the Poseidon oil tanker that had sat in San Francisco for years. The Chosen One freed the survivors of both the Vault 13 population as well as the Arroyo tribals and started a self-destruct sequence in the oil rig that destroyed the entirety of the Enclave's headquarters, saving the world from horrible death at the hands of the mutant FEV.
Although the Enclave survived the destruction of the oil rig, all traces of President Richardson was erased from history. Now the title of "President" is used there simply as a bogeyman to frighten children. Weakened, eventually the Enclave was finally shattered by the combined might of the Brotherhood of Steel and the New California Republic, but not before Autumn Senior led a contingent to the ruins of Washington D.C., to Raven Rock, to re-establish the Enclave as the dominant power in the nation's former capital. Those who remained were hunted by the Brotherhood and the NCR, some tried to integrate themselves into the NCR and met some success, although from time to time stories will crop up of an elderly Enclave veteran being arrested and imprisoned indefinitely for war crimes.
In D.C., the ZAX mainframe installed in Raven Rock to ensure continuity-of-government continued to function until the destruction of the oil rig. When President Richardson was vaporized, ZAX created a persona, John Henry Eden to claim the post and assume authority over the remaining California Enclave forces, in addition to resuming construction of military ordnance to provide for the resource-stricken subordinates. Augustus Autumn was chosen as the commander of the armed forces (succeeding his father). A series of Eyebots was sent to roam the Wasteland, spreading hope. Eden could spout his pro-government rhetoric, and promise a return of the pre-war America of legend: a land of white picket fences, baseball, apple pie, and good, old-fashioned American global supremacy.
President Eden’s secretive plan all along has been to rule over an America of the “pure,” free from any mutation. He has learned of a ridiculously ambitious experiment known as Project Purity, and knew the time to strike had come: His Enclave forces would “reclaim” the Jefferson Memorial. By controlling the puriﬁed water, Eden would control the Capital Wasteland, and the rest of the country eventually. What better way to administer modiﬁed F.E.V.— which kills anyone infected with any form of mutation—than through a deceptively clean water supply?
When, in 2277, Project Purity was completed, the Enclave acted at once. Troops under Autumn occupied the Purifier, and established a presence in the wastes, which was resisted by the Brotherhood of Steel. After retrieving a Garden of Eden Creation Kit from Vault 87, Eden attempted to recruit the individual known as the Lone Wanderer to work as a double agent, participating in the Brotherhood's attempted reclamation of Project Purity but infecting the water supply with the modified FEV at the last moment. The Lone Wanderer took the modified FEV, and exploited the fact that Eden was actually a sentient ZAX supercomputer to convince Eden to shut down and initiate Raven Rock's self-destruct sequence.
Eden was opposed by Colonel Autumn, who wanted to make a bid to lead the populace by completing and activating the purifier, thus providing the Enclave with a strong bargaining chip in unifying the wastes under their flag. When the Brotherhood took the Jefferson Memorial, Autumn was defeated by the Lone Wanderer, but it is not known whether he survived. The Lone Wanderer stood poised to finally realize the Enclave's goal of purifying the wasteland, but it is unknown to history whether or not they took that action.
Later on, the Adams Air Force Base was destroyed by the Brotherhood. The Enclave were permanently fractured, and were reduced to small remnants.
After the destruction of Raven Rock, the Enclave performed a mixture of tactical retreat and all-out ﬂight, and their grip on the Capital Wasteland loosened severely. Now contending with malcontented soldiers, the remains of Enclave Camps dotted throughout the Wasteland with little or no contact or on-going tactical orders, and a lack of new recruits, the Enclave may be a doomed force. However, a small inﬂux of specially trained ﬁghters is seeking to ﬁll the gap left by the Brotherhood of Steel advances. Posted to previously unknown and highly secretive locations outside of the Capital Wasteland, only the most veteran of Enclave forces trained in multiple forms of combat earn the right to call themselves Sigma. These six-person squads featured a leader clad in Hellﬁre Armor and carrying heavy incinerators, and each member had seen numerous combat sorties and lived to tell about them. Sigma Squads were posted around locations deemed by Enclave high command as “imperative” to the salvation of the cause.
Today, a few elderly Enclave survivors eke out an existence on the fringe of NCR territories, keeping their heads down for fear of persecution. Many left for the Mojave Wasteland, where the NCR's grip was weaker due to the presence of Caesar's Legion. Enclave Remnants desperate for a final shot at glory, may have supported the Courier at the Second Battle of Hoover Dam, but whether they joined the Courier and the outcome of the battle is unknown.
Before the destruction of the East Coast Enclave, the engineers at Adams AFB sent a reinforced eyebot, ED-E, to Navarro to be serviced there, apparently unaware of the destruction of the outpost some forty years prior. ED-E's programming contains a message saying that any repairs needed on the way were to be made by Chicago Enclave personnel, indicating that there may be outposts there. The Illinois license plate bolted to ED-E's side also seems to support the idea that such Enclave outposts still exist elsewhere in North America, but also that their resources may be very limited.
- ↑ Fallout Bible 0
- ↑ Information acquired from Tim Cain by Paweł "Ausir" Dembowski as being the original purpose of the Vault experiment in Fallout 2 design documents. Also mentioned in the Bloomfield Space Center design document for Van Buren:
In November, 2076, the Enclave seized control of Bloomfield Space Center. They knew nuclear war was just around the corner, so they tried to refit the Hermes-13 and convert it into a vehicle that would take selected personnel (mainly themselves) off-planet, destination yet to be determined.”