After founding a base in the Capital Wasteland, the Brotherhood of Steel chapter, under the direction of Elder Owyn Lyons, began drifting away from their original mission by prioritising protecting people over technology. This lead to the other chapters cutting off communication. Angered by this, Paladin Henry Casdin, who had fought side by side with Lyons in the scourge of The Pitt, lead other members as they deserted from the Brotherhood of Steel and formed the Brotherhood Outcasts vowing to fulfil the official mission of recovering technology and to try to regain contact with the western chapters. The Brotherhood were wary that an attack could take place, and many Brotherhood soldiers wanted the Outcasts shot or arrested for desertion.
While there were no official battles in this war, whenever members of the two groups encountered each other, which was rare, fighting would break out, only ending when one or the other group was dead. The frequency of their encounters increased after Project Purity went online in 2278 and the Brotherhood of Steel began assisting with aqua pura deliveries across the Capital Wasteland, thus taking them into territory held by the Outcasts.
Though the outcome of this war is unknown, it was notable enough to gain the attention of the Western Brotherhood chapters, though they, themselves, took no action. Veronica Santangelo, a scribe in the Mojave chapter, will make a comment to the Courier about the conflict four years later.