The Nuclear Option (Minutemen)

The Nuclear Option (Minutemen) is a Minutemen main quest in Fallout 4.

Detailed walkthrough
Talking to Preston Garvey after having defended the Castle from the Institute's retaliatory attack will initiate this quest, provided the Sole Survivor has a total of at least eight settlements under their control.

Otherwise the quest Form Ranks will be given instead and must be finished first. Once Garvey considers the Minutemen ready to take on the Institute, he will advise the Survivor to speak to Sturges, who has meanwhile completed his analysis of the Institute data they brought back earlier.

Sturges can usually be found in Sanctuary if he wasn't sent somewhere else. He notifies the Survivor of a possible backdoor into the Institute: an old cooling water tunnel system. He then gives the player a holotape with which they can reprogram the Institute Relay in order to teleport in Minutemen reinforcements. He also mentions insistent radiation warnings about the area you need to traverse, so prepare yourself accordingly.

Opening the map once Sturges finishes his briefing will lead you to the C.I.T. ruins. However, the true destination is only shown by your compass and will eventually lead you to the flooded entrance to the cooling water tunnels at the river bank directly south of Ticonderoga. From there it is only a short walk until the Sole Survivor reaches dry ground again, so no Aquaboy/Aquagirl perk or mirelurk cake is necessary when opting for power armor.

Once you are underground and out of the water, there is an advanced-locked terminal to the left that opens a small room with minor loot. To the right you will find a keypad that needs to be interacted with in order to clear the path forward. Proceed through the large, partly flooded pipe that runs below the small room the terminal opened. The path is mostly linear and crawling with ceiling-mounted laser turrets, mole rats and feral ghouls. It also involves trudging through radioactive water most of the time, so hopefully you heeded Sturges' warning.

Eventually you will reach an elevated walkway with a hard-to-miss expert-locked terminal. From here on the Survivor will encounter hostile synths, two of which can be ambushed through a hole in the wall right next to the terminal. If your hacking skills are insufficient to open the door, proceed along the tunnel until you reach another door. Make your way through the ruins, picking up a fusion core from a generator, an overdue book from an abandoned classroom and several pieces of combat gear along the way, among them a Stealth Boy. Once you arrive at the room where you saw the first synths through the damaged wall, continue through another large pipe on the lower level into the Institute proper.

The pipe brings you directly into the Relay control room where you need to load the Institute relay targeting sequence holotape into the marked console. Doing so will teleport in Garvey, Sturges and several Minutemen. Talk to Garvey and accept the Fusion pulse charge before you take charge of the attack on the reactor. Fight your way through Institute forces, turrets and a Sentry bot, the latter of which can be destroyed before it powers up if you are quick enough (alternatively, using a nearby terminal will allow you to power it up before entering its field of view and causing it to become hostile to the synths in the room). After reaching an iris-like hatch in the floor and jumping down to the next-lower level, pick up another fusion core from the nearby generator before proceeding to the Bioscience facilities. Dispatch all hostile synths and beware the synth gorillas that get turned loose, should the Sole Survivor venture too close to their compound.

The next area contains a lot of hostile synths including several coursers that usually attack under the cover of their Stealth Boys. The Survivor will also encounter at least one named legendary synth here. Once all enemies have been taken care of, Sturges will direct you to the Advanced Systems department, only to tell you that it has been locked down and needs to be opened from the Director's personal terminal. Use the large central elevator to reach Father's quarters where he lies dying. Talk to him if you feel like it; convincing him to help you by passing an easy charisma check will provide the Sole Survivor with the password for his terminal. The terminal's password is also available in the desk to the left of the computer.

Alternatively, simply hack the novice-locked computer in order to use it to lift the security lock down. You can also make the rest of the mission easier by shutting down some of the synths (persuade Father for this password), as well as opt to fulfill the optional objective by engaging the Evacuation Protocol BD-2, which is highly recommended if you plan on continuing your work with the Railroad. If you don't evacuate, the entire Railroad will turn hostile as soon as you meet them again. Also, Garvey will hate not giving the evacuation order. Once you are done, head for the Advanced Systems facilities and the reactor.

Securing the reactor involves a tough fire fight in close quarters. Again you will encounter two named legendary synths Z4K-97B and A-2018 that wield powerful weapons and carry the reactor terminal password. Make sure to shut down the reactor and initiate the radiation purge before you enter to place the fusion charge. Talk to Garvey and let Sturges teleport you to the relay control room where the Sole Survivor encounters S9-23. Deal with the kid as you see fit, then talk to Sturges. This is your last chance to return to collect whatever you might have missed in the Institute. Choosing to abandon synth Shaun will prevent the Sole Survivor from receiving Shaun's unmarked quests, making the Wazer Wifle unobtainable.

Once you are ready, tell Sturges so and step into the Relay. You will then be teleported to the roof of the Mass Fusion building. Pressing the detonator in front of you will blow up the Institute's reactor and initiate the epilogue cut scene. Talking to Garvey afterwards finishes the mission. Should you have made enemies with the Brotherhood of Steel by this point, the next mission With Our Powers Combined will usually start as soon as you get in Garvey's dialogue range again.

Keeping all three factions alive
To get the most out of all main faction questlines while finishing the game for the Minutemen, do the following:


 * 1) Join the Minutemen by saving them in Concord and helping them rebuild Sanctuary Hills, retake The Castle including its Old Guns and set up a total of at least eight settlements throughout the Commonwealth.
 * 2) Continue the main quest up to Institutionalized. Be careful not to alienate Father by acting consistently hostile towards him during your first meeting or he will ask you to leave.
 * 3) Give the holotape from Inside Job to Sturges first. This is only available if you build the Signal Interceptor with the Minutemen in The Molecular Level.
 * 4) If you haven't killed them, assist The Railroad until you are told "to continue working with Father" during Underground Undercover. Keep in mind that you will fail this quest if you decide to keep the Brotherhood of Steel alive.
 * 5) Help the Brotherhood of Steel up to the quest Blind Betrayal. Make sure to receive and complete the quests Duty or Dishonor and A Loose End for Lancer-Captain Kells before you finish Blind Betrayal, or you might miss out on two of the very rare unique Power Armor pieces in the game.
 * 6) Do any and all quests you can find for the Institute up to Mass Fusion.
 * Do something to get Banished from the Institute, like killing a named scientist or Father. Or accept Mass Fusion but instead report it to the Brotherhood, which will immediately start Spoils of War. Complete Spoils of War for the Brotherhood and this will automatically fail both the Institute and some of the Railroad questlines and allow you to lead the Minutemen to victory while still having the Brotherhood of Steel around, resulting in three of four main factions surviving the end game (although you still have to be careful to keep this peace while pursuing more of their respective quests).


 * Do not proceed through Brotherhood quest straight away after gaining access to the Institute, except for From Within and Duty or Dishonor. Instead follow Institute questline until you reach Mass Fusion, since this is the only way to get Spoils of War without starting Tactical Thinking. Also, do not hand in Blind Betrayal to Maxson before finishing off the side quests from Kells, (The Lost Patrol, Duty or Dishonor, and A Loose End) since talking to Kells afterwards will proceed Tactical Thinking to the point you are hostile to The Railroad.


 * It is impossible to report the Institute's advance towards Mass Fusion if you have already turned in Blind Betrayal, as Ingram will not speak to the player, except to direct them to Kells to begin Tactical Thinking, which instantly makes the Railroad hostile. Using Console Commands to set Tactical Thinking to complete, and to instigate Spoils of War, makes completion of Spoils of War, completion of Blind Betrayal, and a three-faction peace still possible. It is still possible to complete Blind Betrayal immediately after having completed Spoils of War.


 * If you do not issue the evacuation order before leaving, The Railroad including Deacon will become hostile the next time the player speaks to Desdemona.
 * Depending on how the player completed quests prior to this, this is the only ending in which both The Brotherhood and The Railroad can survive. This outcome may be completely unintentional, as characters in either faction will speak and as if only they and the Minutemen survived; for example, P.A.M. will still offer A Clean Equation or High Ground quests, as if the player had previously destroyed the Prydwen and sided against the Brotherhood.
 * On completion of the quest there will be a long message broadcast over Radio Freedom detailing the events and thanking the 'General' and other Minutemen for their actions.
 * After this quest is completed, the Brotherhood of Steel and Railroad will treat it as if their main questlines have been completed. This means Glory is considered to be dead (even though she is still alive), and no main quests can be issued from either faction.

Bugs

 * If the player has completed Underground Undercover Z1-14 may be in the Relay Control Room and be hostile to the minutemen when they arrive, but essential so he cannot be killed, making it difficult to speak to Preston Garvey. (disabling Z1-14 with console commands fixes this and seems to have no repercussions)
 * If the player did not relay to the top of the Mass Fusion building to start the Mass Fusion quest, or fly there at the beginning of Spoils of War, relaying to the roof of the Mass Fusion building at the end of this quest may activate the same trigger that turns the Brotherhood of Steel hostile at the beginning of the Mass Fusion quest.
 * When the player teleports to the top of the Mass Fusion Building and talks to Preston Garvey the dialogue will never end and keep looping itself, making the quest impossible to finish. If you speak to him and then fast-travel to another location, the quest should complete. (tested on PS4 only)