Enclave

The Enclave is the main villain organisation in Fallout 2.

Overview
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 the oil rig 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 United States government officials leave their posts to take refuge in a number of secret locations around the world. Among them was the Poseidon Oil rig. Here, the President himself set up a secret base from which the U.S.A. could continue to exist and wage war on China, with the eventual goal of retaking the continental United States.

The Enclave essentially represents those parts of the US government that managed to escape the Great War. The Enclave's scientists went continued to do research on armor and weapons after the War and thus have even fancier toys than the Brotherhood of Steel, who only have U.S. Military standard issue from when the Great War broke out.

The Enclave's Plan
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, though, 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 rather impressive Vertibirds, the Enclave sent out scouting parties all over California, the closest state to the Oil Rig.

What they found there scared them considerably: mutancy was rampant. The Enclave scouting parties arrived in California after Fallout 1 ended, and so saw super mutants and ghouls littering the land and the destruction and ravages they caused. When this was reported to the higher ups at the Enclave, it was decided that all the mutants would have to go. It occured 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 (indeed, most people living in the wasteland were inoculated with an airborne mutation of FEV immunizing them to the full effects of the real serum). These mutants too, then, would have to be destroyed before true humanity, true America, could once again lay claim to the mainland.

Reconaissance and exploration of California continued: the Enclave didn't have any means of carrying out their genocidal ambitions short of 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. FEV was what created the super mutants that most threatened the Enclave, and it would eventually come to be the Enclave's solution to these same mutants.

The Vaults were funded by the U.S. government and, accordingly, the government had control over them. From the Oil Rig, the Enclave could monitor and control Vaults all across America.