On October 20, 2077, Captain Maxson declared his unit in full secession from the United States, attempting to force the government to respond to the situation at Mariposa.

Erin Shellman held out the longest, almost convincing the captain that the experiments were really ordered by the government. Subsequent scientist interrogations invariably ended in executions. His position was further reinforced on October 15, when Colonel Spindel committed suicide as his men broke into his office. This established Maxson as the leader of the rebellion. When Maxson refused to believe him, the scientist lost his nerve and started screaming how he was just following orders and that he was also a military man.

Anderson explained that the testing at the facility was sanctioned and, in fact, ordered by the government, as he outlined the experiments to the captain. The first scientist to be interrogated by Captain Maxson was Robert Anderson, chief researcher of the research team at Mariposa. When two days later, on October 12, the captain stopped a soldier from murdering a scientist, he ordered the scientists to be interrogated. The soldiers were screaming for blood and became increasingly aggressive. Colonel Spindel suffered a nervous breakdown, locking himself in his office, leaving Captain Maxson to handle the deteriorating situation at the base. This secrecy backfired shortly before October 10, 2077, when soldiers stationed at the base discovered the human testing that was going on at the base, made worse by the fact that the scientists were using military prisoners as test subjects. They were not informed of the nature of the research. The security team was transferred to the newly constructed base as well, to provide protection for the research going on within the facility. On January 7, 2077, all Californian FEV research was moved to the newly-constructed Mariposa Military Base from the West Tek facility to commence testing of the virus on human subjects. The United States Defense Department, in fear of international espionage, moved a military team under the command of Colonel Robert Spindel and Captain Roger Maxson onto the site to secure and oversee the project, now dubbed the FEV ( Forced Evolutionary Virus) project. In 2076, the NBC division of West Tek achieved breakthrough results in the Pan-Immunity Virion Project.

In Fallout 2, the base can be found ten squares east and twenty-seven squares south of Arroyo.

In Fallout, Mariposa Military Base can be found thirteen squares west of Vault 13.

Fallout 4 military base mod