I Am Become Death

I Am Become Death is a main quest in Fallout 76.

Quick walkthrough
Once entering a silo bunker, be prepared for many robot enemies. Eventually enter a high radiation zone in the silo's reactor chamber, which will linger until the reactor is shut down and fully repaired to prevent further radiation leakage.

Once having access to the silo's Launch Control Center, enter a nuclear keycard into the marked terminal, the decrypted Nuclear launch code in the terminal opposite, then use the main console between them to select the area to be struck by the nuke, confirm, and watch missile launch.

Optional objective: Launch the nuke at fissure site Prime to summon the scorchbeast queen.

Detailed walkthrough

 * After gaining the rank of general and being appointed to the Joint Chiefs, Vault Dwellers need to head to the Whitespring Congressional Bunker command center. MODUS will proudly introduce the last section of the facility and invite player characters to familiarize themselves with the automated training for officers in charge of Appalachia's automated nuclear arsenal.
 * The quest requires Vault Dwellers to complete several steps. Fortunately, the tracking terminal at the command center allows them to trigger a surveillance sweep that will give them the rough location of either a code piece or a keycard convoy (starting the Hide and Seek and Destroy repeatable quest).
 * First, the codes. Each of the three silos (at Site Alpha, Site Bravo, and Site Charlie) has its own individual launch code. These are gathered from ghoulified or scorched officers with a field radio strapped to their back. Killing them will yield a single letter/number pair necessary for decryption. The codes are automatically added at the command center and will display a seemingly random string letters and numbers. Figuring out the word also produces the code for launching a nuke.
 * If Vault Dwellers want to ensure they have the correct code, they need to access the archival terminal in the command center armory and read Gen. Santiago's notes to learn about the Fujiniya Intelligence Base. Inside, they need to locate the lone terminal behind the blue fusion generators and use it to input the password from the bunker. This will produce a usable nuclear launch code.
 * Second, to input the code, Vault Dwellers require a nuclear keycard. These are ferried via automated cargobot convoys across Appalachia and collecting them is as simple as shooting down the cargobot, though taking out its vertibot escorts will make it easier as the vertibots shoot at anything they deem a threat to the cargobot.
 * Third, access to the silo. This is covered under Mission: Countdown.
 * The quest completes upon launching the first nuke.
 * Optional objective is to nuke fissure site Prime, thus summoning the scorchbeast queen and triggering Scorched Earth.

Behind the scenes
The title of the quest is a reference to a passage from the Hindu scripture Bhagavad Gita: "I am become death, the destroyer of worlds." This line was quoted by J. Robert Oppenheimer after the world's first successful nuclear device test.