|The following is based on Van Buren and has not been confirmed by canon sources.|
The Circle of Steel is a splinter faction of the Brotherhood of Steel.
In an effort to end the war with the New California Republic once and for all, the Brotherhood began to use newly discovered subversive technology known as Stealth Boys. These devices could create a field of energy that would bend light around the user, thus making the user virtually invisible to the untrained eye. This allowed Brotherhood operatives to penetrate deep into NCR territory for the gathering of intelligence. However, it was soon discovered that the devices had severe side effects. Paranoia, delusions, and eventual schizophrenia were the major ones. The Brotherhood disallowed the use of Stealth Boys and once again fell behind in their war effort.
The side effects of these devices were not discovered until the team using them had already begun to feel their effect. When the team was disbanded, paranoia over the reason began to set in and the team plotted against their leaders. They stole the Stealth Boys, fled the bunker as deserters, and formed a covert group known as the Circle of Steel. The goal of the Circle is to recover lost technology and rebuild the glory of the Brotherhood at any cost.