Precipice of War

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Precipice of War is a Railroad main quest in Fallout 4. It is the follow-up from Underground Undercover and is part of a chain of quests, all of which are tied together, to an alternative method of completing End of the Line.

Quick walkthroughEdit

Railroad main quest: Precipice of War
Warn Desdemona.
Defend Railroad HQ.
Talk to Desdemona inside HQ.
Secure Old North Church.
Speak again with Desdemona, now near the church exit.
Meet Tinker Tom at the Cambridge police station.
Eliminate all Brotherhood forces.
Talk to Tinker Tom.
Defend the vertibird.
Talk to Deacon.
Reward: 500 XP
Leads to: Rockets' Red Glare

Detailed walkthroughEdit

Upon warning Desdemona of the Brotherhood of Steel's impending attack, it begins immediately upon delivering the warning. Defeat the Brotherhood soldiers that attack from the route leading to the escape tunnel. After they are dead, speak with Desdemona, who informs the player that the catacombs are the only way to escape. Glory has already gone ahead to secure passage, and Desdemona asks the player to assist.

Entering the catacombs, Glory has been grievously wounded. Regardless of how the player answers her, she succumbs to her wounds. Two Knights, one in power armor, the other in BOS combat armor, will burst through the sealed entryway with explosives. Kill them and then continue back through the crypt, fighting Initiates and Knights along the way. Up on the main floor of the church, another unit of Brotherhood Initiates, Knights, and Aspirants will be waiting. They will all need to be eliminated.

Note: Paladin Brandis may be among the enemies here, if he was convinced to return to the Brotherhood during The Lost Patrol. He has unique gear which can be obtained by shooting out the fusion core on his power armor, but he is armed with a minigun and is considerably more dangerous than the average enemy here.

Once all of the soldiers are dead, Desdemona and the others will enter from the catacombs. Grieving the loss of Glory, they note that the Brotherhood underestimated the Railroad's strength and will attack again with a much greater force, thus the Old North Church will not be safe until they are eliminated as a whole. Operation "Red Glare", the destruction of the Prydwen, is a go. To carry it out, the player must steal a vertibird from the Cambridge Police Station. Head there immediately and rendezvous with Tinker Tom.

Outside of the station, Tom mentions that the vertibird is still on the roof and all Brotherhood personnel must be eliminated (including Haylen and Rhys). Enter the station and open fire, making sure to check every room, including the garage, which might be closed from the outside. Once they are all dead, head to the roof and kill the remaining soldiers. Tom hands over an explosive charge to affix to the tanks of hydrogen onboard the Prydwen, which will detonate and ignite the hydrogen in the envelope, bringing the airship crashing down.

While Tom preps the vertibird, an enemy vertibird will arrive and attack. Shoot it down or kill everyone aboard, then talk with Deacon to complete the quest. The quest Rockets' Red Glare will then begin.

Quest stagesEdit

101 Warn Desdemona
200 Defend Railroad HQ
300 Talk with Desdemona
400 Secure the Catacombs
500 Secure the Church
600 Talk with Desdemona
700 Meet Tinker Tom at the Police Station
800 Eliminate Brotherhood forces
900 Talk with Tinker Tom
950 Defend the vertibird
1000Quest finishedIcon checkTalk with Deacon


  • If Deacon isn't the current companion, he will leave whatever residence he is located at, and follow Tom throughout the mission.
  • The Final Judgment weapon can be obtained by going to The Prydwen and kill Elder Arthur Maxson.
    • Note, he will not spawn until you have placed the three explosives.
  • The mission can be completed with "no alerts" if the Brotherhood has been killed off beforehand.
  • If Duty or Dishonor has been completed by convincing Initiate Clarke to turn himself in and he hasn't subsequently been let out, he will be locked up in Cambridge Police Station. Clarke is non-hostile and can be released without incident.
  • One may have to wait for Deacon to show up in order to talk to him. The map will show him somewhere along the route between Old North Church and the bus stop to the North of Cambridge Police Station. Attempting to quick travel to his location will only result in him being further along the route and no longer near where quick-traveled to. The Sole Survivor can sit to wait a couple hours at the bus stop and he will show up.
  • If you get stuck and are unable to secure the police station despite all enemies being dead, try killing Haylen at Waypoint Echo (if you had started the quest Liberty Reprimed before betraying the brotherhood.)


  • [platforms tag needed] Tinker Tom will be sitting on the ground after taking too much damage and the quest will not progress unless he goes to the Vertibird. It will say "Defend the Vertibird" but Tinker Tom is bugged and so the attacking Vertibird will not appear to advance the quest. This can be fixed by fast traveling to another location, and then back again. [verification overdue]
  • [platforms tag needed] Shooting the attacking Vertibird with a weapon that can cripple an enemy's legs thanks to its unique prefix will cause the Vertibird to become indestructible - its health can be depleted but it won't crash, thus preventing the mission from progressing to the next stage. Make sure to bring a powerful backup weapon if the primary gear features this prefix.[verification overdue]
    • Another way to fix it is to walk around and/or back and fourth below the Vertibird, this may cause it to crash.
  • [platforms tag needed] Even if you shoot down the Vertibird, the quest can become bugged and not progress past "Defend the Vertibird". Entering setstage 2c8cb 11000 with the enemy Vertibird targeted will progress the quest correctly. [verification overdue]
  • [platforms tag needed] The church may be impossible to secure even after killing all the Brotherhood members inside.
    • The setstage command also does not seem to fix this.
  • At Cambridge Police Station, killing some members of the Brotherhood of Steel will count towards your Murder statistic in your Pip-boy, despite them clearly being hostile towards the player.
  • pcIcon pc If the Brotherhood didn't become hostile during Mass Fusion, either by activating the fast travel point manually and thus skipping the confrontation or by using the console to bypass that stage of the quest, there will be at least one Brotherhood soldier in the Church friendly to the Sole Survivor and fighting against the other Brotherhood soldiers. Killing them will make the quest progress and will not count as Murder in your Pip-Boy.

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