Defiance Has Fallen

 is a quest in Fallout 76. It unlocks after reading the "Fort Defiance" post in the terminal inside Abbie's Bunker.

Synopsis
Years ago, the Brotherhood in Appalachia sent out a cryptic message saying that Defiance has fallen. Nobody outside the Brotherhood knew what that means - it's up to Vault 76 dwellers to figure out the mystery.

Walkthrough

 * The first step in finding out what Defiance means and what happened to the Brotherhood lies at Camp Venture (this part can be skipped if the player already has the location of Fort Defiance).
 * Searching Camp Venture will require getting into the command center. The locked door is password-protected and will require the players to head to the storage and supplies building and open the locked room in the basement. The key is located in the building south of the command center, inside the locker. After opening the door, the note should be inside on the table.
 * With the password, players can enter the command center. The note detailing Fort Defiance's location is on the table to the right (Letter to Tommy).
 * Fort Defiance is located southwest of Camp Venture, and roughly west of Watoga. The monorail elevator is a good navigational aid, as it's near the Fort.
 * Once at Fort Defiance, formerly the Allegheny Asylum, the player has to activate the power for the facility. This requires navigating the treacherous asylum, full of rather ornery ghouls. The first step requires activating the circuit breaker located in the derelict wing of the asylum (the route is linear and mostly requires getting higher and further through the ruined rooms). The Final Stand note, found near the locked room all the way back at the entrance, will complete the quest and start the next one.