Fallout 4: Brotherhood of Steel Route Guide - From Joining to Ending

※This article is current as of June 2, 2026. Fallout 4 is not a live service game, so it does not have a seasonal system like Fallout 76. However, a free next-gen update for PlayStation 5 and Xbox Series X|S was released on April 25, 2024. This update includes the addition of Performance Mode (up to 60FPS) and Quality Mode, improved stability, and quest fixes. Furthermore, a new questline called Enclave Remnants and several Creation Club contents were added for free. This article is written based on current information.

The Brotherhood of Steel (B.O.S.) is an organization that seeks to bring order to The Commonwealth with iron discipline and overwhelming military power. Based out of the massive airship Prydwen, many players will sympathize with their ideology of monopolizing technology and eradicating Synths and mutants. This article provides a complete guide to joining the B.O.S., rising from Knight to Sentinel, and securing the future of The Commonwealth with them. Ad Victoriam!

B.O.S. Main Quest Overview

Path to the B.O.S.: From Joining to Full Member

Your involvement with the B.O.S. begins naturally as you progress through the main quest. We will explain the steps to becoming a member of the Brotherhood of Steel, who bring order to The Commonwealth.

1. Encounter at Cambridge Police Station

1. After completing the main quest "Reunions" and defeating Kellogg, the giant airship Prydwen will appear overhead.
2. Receive "Military Frequency AF95" on your Pip-Boy to start the quest "Fire Support".
3. Head to Cambridge Police Station and assist Paladin Danse and B.O.S. Scribes who are under attack by a horde of Feral Ghouls.
4. After the battle, speak with Danse to receive the quest "Call to Arms". Accompany him to ArcJet Systems.

• Easily Missed Detail: In the room with ArcJet Systems' engine core, on the terminal's floor, you will find a "Tesla Science" magazine. Don't forget to collect it.

2. Boarding the Prydwen and Formal Induction

Upon completing "Call to Arms," Danse will offer you a chance to join the B.O.S., initiating the faction quest "Semper Invicta." However, your formal induction is still some time away.

1. Progress through the main quest until the Prydwen docks at Boston Airport, at which point the quest "Shadow of Steel" will automatically trigger.
2. Report to Paladin Danse, then board a Vertibird with him and travel to the Prydwen.
3. Inside the airship, you will meet Elder Maxson, the supreme leader. After your conversation, you will be formally granted the rank of "Knight" and become a full member of the B.O.S.
4. At this point, you will be assigned a private cabin and a full set of "T-60 Power Armor," and Paladin Danse will become available as a companion.

As a Knight of The Commonwealth: Main Quests and Vertibird Unlocked

As a Knight, the player is tasked with eliminating threats rampant throughout The Commonwealth. Here, we will cover important mid-game quests and the thrill of utilizing Vertibirds, a highlight of the B.O.S. route.

Unlocking Vertibird Transport

In the quest "Show No Mercy," you are ordered to clear Strong's Stronghold of occupying Super Mutants. It's an exhilarating mission where you board a Vertibird from the Prydwen and clear out enemies with its mounted Minigun. Completing this quest rewards you with a "Vertibird Signal Grenade." By throwing this outdoors, you can summon a Vertibird at any time, allowing you to use it as an alternative to fast travel. Since you can attack ground enemies with the Minigun while traveling, it becomes a very powerful movement and combat support tool.

"Blind Betrayal": Deciding Paladin Danse's Fate

The most dramatic quest in the B.O.S. route is "Blind Betrayal." The shocking truth is revealed: Paladin Danse, who has served the B.O.S. for many years, is actually a Synth who escaped from the Institute. Elder Maxson orders the player to execute Danse, forcing a critical decision.

• Execute Danse: Follow B.O.S. discipline and kill Danse. Your standing with Elder Maxson will improve.
• Save Danse (Recommended): Speak with Danse and either convince him to flee The Commonwealth, or persuade Maxson to acknowledge his past contributions and report to the B.O.S. that he died, allowing him to survive. If Danse survives, you can continue to have him as a companion, and when his affinity is maximized, you will gain the powerful Perk "Know Your Enemy" (+20% damage to Synths, Feral Ghouls, and Super Mutants).

This decision does not affect the ending branches, but it is a crucial turning point in the story and significantly impacts your relationship with companions.

Ad Victoriam! The Final Battle Towards the Ending

The story escalates into an all-out war with the Institute. The choices you make from this point on will decisively determine your relationships with other factions, so proceed with caution.

Confirmed Hostilities

• Tactical Thinking: Upon accepting this quest and receiving the mission to destroy the Railroad headquarters, you will become permanently hostile with the Railroad. Your companion Deacon will also leave and become hostile.
• Spoils of War: Once you board a Vertibird from the Prydwen to seize the Beryllium Agitator from the Institute, you will become permanently hostile with the Institute.

Advance with Liberty Prime

In the quest "Ad Victoriam," you will advance towards the Institute's stronghold alongside the reactivated colossal war machine, "Liberty Prime." His overwhelming firepower and patriotic lines are among the most iconic scenes in the Fallout series. If you destroy the Institute's reactor in the final quest "The Nuclear Option," the B.O.S. victory is confirmed, and you will reach the ending. After the ending, the quest "A New Dawn" will trigger, and Elder Maxson will bestow upon you the rank of "Sentinel," the highest in the B.O.S., along with a custom T-60 Power Armor equipped with a jetpack.

Recommended Build for B.O.S. Soldiers (Power Armor & Heavy Weapon Specialist)

To fully enjoy the B.O.S. route, a build that utilizes their iconic Power Armor and heavy weapons is ideal.

Example S.P.E.C.I.A.L. Starting Allocation

• Strength: 9 - Essential for "Heavy Gunner," which increases heavy weapon stability and damage, and "Pain Train" for Power Armor charge attacks.
• Perception: 3 - Increase to 4 with a Bobblehead for grenade arc display, etc.
• Endurance: 5 - Ensures durability.
• Charisma: 3 - For "Lone Wanderer" when fighting without companions.
• Intelligence: 9 - Crucial for "Nuclear Physicist" to extend core lifespan and for obtaining various modification Perks like "Armorer," "Science!," and "Gun Nut."
• Agility: 1
• Luck: 1

Important Perks

• Heavy Gunner (S): Maximizes heavy weapon damage, such as Miniguns and Gatling Lasers, up to double. Prioritize acquiring this.
• Armorer (S): Essential for advanced Power Armor modifications. Allows you to add defensive stats and special effects.
• Nuclear Physicist (I): Extends fusion core duration by up to double. This is a lifeline for dramatically reducing Power Armor operational costs.
• Science! (I): Required for Power Armor jetpack modifications and energy weapon modifications.

Recommended Equipment

• Weapons: The "Gatling Laser," purchasable from the B.O.S., is excellent in both ammo efficiency and damage. Early on, the unique weapon "Righteous Authority" received from Paladin Danse is also a powerful option.
• Armor: The "T-60 Power Armor" obtained through quests will be your main armor. Apply B.O.S. paint and reign over The Commonwealth as a Sentinel.

Conclusion

The Brotherhood of Steel route is an epic narrative that establishes an iron order in The Commonwealth, backed by overwhelming military power. The experience of donning Power Armor, unleashing Minigun fire from a Vertibird, and trampling enemies alongside a giant robot is unmatched by other factions. The deep role-playing, including your friendship with Paladin Danse and the conflicts with the B.O.S.'s proclaimed justice, is also a major draw. Refer to this article and seize the future of The Commonwealth with the B.O.S. Ad Victoriam!