Mission: Countdown

Mission: Countdown Alpha, Mission: Countdown Bravo, and Mission: Countdown Charlie are repeatable main quests in Fallout 76 that trigger the launching of an intercontinental ballistic missile to a map location selected by the player character.

Detailed walkthrough
Before starting this quest, the player character will need to acquire at least one nuclear keycard and the decrypted weekly launch code for a silo bunker.

Upon entering a silo bunker (either Site Alpha, Site Bravo, or Site Charlie), be prepared for many robot enemies. Bring energy-resistant gear and energy weapons. A highly radioactive room will also be within the silo.

The first part of the quest will require the player to find a way past the first set of laser grids, by means of forging a biometric ID card. Old biometric ID cards can be found through the door to the left after first stepping out of the elevator. The majority of the silo will be filled with laser turrets and robots, but with a Level 3 hacking skill, and using terminals scattered throughout, the robots and turrets can be programmed to shut down or by removing targeting restrictions, made to turn on one another.

In the next room are two terminals that the player must read to acquire information on security protocols, giving instructions for creating new biometric ID cards. After acquiring an old biometric ID Card, the player should locate an ID card eraser and follow the instructions on the terminal. Afterwards, following the mission markers will take players to biometric scanners which the player will enter. Then, a nearby terminal will fabricate the new card. Activating the card will deactivate the first laser grid.

Through the deactivated laser grid and the silo corridors is the Power House and another terminal to handle the robots and turrets. Here, the player should locate a terminal with instructions in the room with the nuclear reactor. Using the terminal will shut down the reactor for 3 minutes and allow the player to repair sections of piping around the room. These repairs do not require any materials to complete. Prepare to deal with radiation from the reactor, as well as a variety of robots that will periodically spawn. Once the reactor restarts, the quest will proceed to the next stage.

In the next stage of the quest, the player will follow quest markers to the control room, where they will need to destroy dozens of mainframe cores. Destroying the cores in one room will deactivate nearby laser grids and grant access to more cores and laser grids. There are more terminals with aforementioned robot and turret controls, but the player should be prepared to fight higher level robots such as assaultron dominators. After destroying all cores, follow the markers to the next area.

The following stage of the quest involves crafting 15 replacement mainframe cores or finding intact ones around the room. Repairs can be made at a nearby tinker's workbench with circuitry and steel. Replacing all 15 cores and using the terminal to open a security door will take the player to the launch silo and the final part of the quest.

Inside the launch silo is a nuclear missile. Past this, through a door and up a few flights of stairs is the control room. The player will be promoted to initiate launch prep. Doing so will spawn friendly launch control robots which must be protected as the carry out their corresponding tasks. This process tends to be rather tedious with the robots slow moving and the enemies numerous. Successfully defending the launch control robots will complete the quest.

Once the quest is completed, the player character will be prompted to select a blast zone target location within Appalachia for the nuclear missile. Some lower-level areas located in the western portion of Appalachia are considered to be within a "protected zone" and cannot be targeted. If fissure site Prime is targeted, the scorchbeast queen will be spawned and the Scorched Earth quest will begin. Targeting other locations will spawn higher level versions of whatever enemy is normally present in that area.