Lyons passed away in 2278, and leadership passed to his daughter Sarah Lyons. However, with the assistance of the Lone Wanderer, the Brotherhood ended the Enclave's presence in the known region driving them first from Project Purity and then from their final holdout at Adams Air Force Base.Дespite the Brotherhood's success with Project Purity and the war against the Enclave, the organization continued to struggle. They seized Project Purity, then set up outposts in Washington, D.C., and the surrounding wilderness. It was in this weakened and isolated state that it was possible for the Enclave, having relocated from New California as well, to re-establish a base of continual operations at Raven Rock, to make its move. The chapter suffered a further setback when a number from within their ranks left in protest to form the Brotherhood Outcasts.

When the Elders in Lost Hills learned of these new priorities, they cut off all support to the chapter, though they still considered it as part of the Brotherhood. The Brotherhood's primary directive was to recover and preserve advanced technology, however Elder Lyons' detachment took on a more humanitarian approach towards non-hostile wastelanders. The Brotherhood's treatment of people in Pittsburgh and in Washington marked a characteristic trait of Elder Lyons' leadership. The discovery earned Owyn Lyons a promotion to elder and a change in his orders: instead of returning to the West Coast, they would establish a permanent presence in the area in the location. Their investigation of the Pentagon uncovered a remarkable cache of technology, including the four-story-tall robot known as Liberty Prime. Attacking head-on, they drove the mutants into the ruins of Washington, D.C., and earned the favor of the local population. On their arrival, the wilderness outside the city was overrun by super mutants. During the Scourge, Lyons' forces suffered only one casualty: Initiate Ishmael Ashur, who was buried in rubble during the fighting and presumed dead.

Lyons' contingent left the city with approximately 20 children in tow, who would later be initiated into the Brotherhood. In a single night, the Brotherhood swept through the city from their staging area at Mount Wash, and eliminated any resident who put up a fight. On their way to the Capital Wasteland, the Brotherhood's forces came across the ruins of Pittsburgh, Pennsylvania, a chaotic and violent city.

Brotherhood of steel concept art