While the FEV was released into the wasteland, the soldiers and their families inside Mariposa survived the bombing. On October 23, 2077, the Great War between the United States and China led to the virtual destruction of Earth. All of the soldiers brought their families into the base for protection. As morale in the base collapsed and the unethical experiments turned chaotic, Maxson took charge, executed the scientists, and on October 20 declared his desertion from the United States military.

Maxson was horrified to discover that the experiments being conducted by West-Tek involved using military prisoners as unwilling test subjects for the Forced Evolutionary Virus (FEV). On January 7, 2077, the facility was relocated to the Mariposa Military Base. In 2076, Captain Roger Maxson of the United States Army was assigned to monitor a West-Tek facility working on a government contract in California. After becoming a quasi-religious organization dedicated to preventing technology from falling into the wrong hands, their conflict with the New California Republic led to the western chapter being almost completely wiped out. The Brotherhood of Steel originated on the West Coast as an outgrowth of the United States military on the advent of the Great War.