Brotherhood Civil War

The Brotherhood Civil War was a conflict between the Brotherhood of Steel and a splinter group, the Brotherhood Outcasts. The conflict began in 2276, following a drastic shift in mission profile by Owyn Lyons. Soon after, a large group of Brotherhood loyalists, led by Protector Henry Casdin, broke off from the chapter and continued the Brotherhood's mission on their own.

By 2287, the war had been over due to changes within the leadership of the chapter.

Background
 As Owyn Lyons slowly changed the profile of the mission to DC from gathering and processing pre-War technology to endeavours he considered beneficial to the local populace, discontent began to rise among his ranks. The dissatisfaction reached a boiling point in 2276 when Paladin Henry Casdin openly defied the Elder's orders and rallied his followers, secured large amounts of weapons and equipment and left the Citadel.  Branded as outcasts and struck from the Codex, the loyalists formed a new chapter, bearing the name "Outcasts" as a badge of merit, along with the black/red paint-job on their power armor units. They secured a new base of operations in Fort Independence near the ruined city of Fairfax and continued their original mission of securing technology.

Development
The Outcasts have many advantages over the Brotherhood of Steel when departing the Citadel, they took a large amount of supplies and military ordnance with them, leaving the chapter in a critical condition. Furthermore, all of the loyalists are all veterans of the Brotherhood, are trained in the use of advanced weaponry, and have years of experience and wasteland travels behind them. On the other hand, the Brotherhood chapter consists of a mix of original Brotherhood members and hastily trained local recruits.

Despite the advantage, Outcasts do not seek to exploit their advantage and refuse to openly attack the Brotherhood. They focus on their mission and their long-range patrols in search of lost technology make the wasteland much more secure, as they exterminate any threats with extreme prejudice but do not engage non-hostile humans unprovoked.

However, if confronted with a Brotherhood patrol, the Outcasts will attack and fight until either side is dead. The frequency of these encounters increase 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.

Legacy
Veronica Santangelo, a scribe in the Mojave chapter, will comment about the conflict four years later. Sometime before 2287, the death of Lyons and his daughter leads to Arthur Maxson taking over the eastern Brotherhood and reintegrating the Outcasts.