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Liberty Prime full system analysis. All systems: nominal. Weapons: hot.Liberty Prime

Ad Victoriam is a Brotherhood of Steel main quest and an achievement/trophy in Fallout 4.

Quick walkthrough

Brotherhood of Steel main quest: Ad Victoriam
Speak with Proctor Ingram.
Plug in the Beryllium Agitator.
Turn on Liberty Prime.
Follow and defend Liberty Prime.
Clear the courtyard.
Enter the tunnel.
Reward: 500+ XP
Leads to: The Nuclear Option

Detailed walkthrough

After destroying the Railroad and getting the Beryllium Agitator, speak to Proctor Ingram at the Boston Airport. She will now allow the Sole Survivor to power up Liberty Prime. Go to the top of the gantry and plug the agitator into Liberty Prime. After that, return to Ingram and press the button. Liberty Prime will activate, leave the gantry and start walking towards the C.I.T. ruins, with the Brotherhood of Steel personnel saluting it as it walks away.

The player character must now follow Liberty Prime as it walks through the ruins of Boston to reach the Institute. As it reaches the East Boston Preparatory School, synths will be teleported to attack it. From that point on, various enemies will be encountered: raiders, Super Mutants (including one or two behemoths), and synths. Due to a broken bridge, Liberty Prime will have to cross through the water in order to continue. It will then reach the Bunker Hill monument. After paying its respects at the memorial, it will continue its journey through the streets of Boston.

Liberty Prime will annihilate everything thrown at it, using its powerful eye laser as well as nukes, even effortlessly crushing the behemoths that will attack the robot near Ticonderoga. Do note however that, unlike in Take it Back!, Liberty Prime will mostly use its Mark 28 bombs rather than its eye laser; thus, it is advised to stand back from Prime's enemies and let it destroy them, as one may get caught in the blast radius of one of Prime's bombs, which will deal a significant amount of damage. Since Liberty Prime is entirely immune to its own weaponry, it has no qualms about using the nukes at point-blank range. During the trip to the Institute, one will be followed by a small group of Brotherhood of Steel knights, comprised of Knight Lucia and a few unnamed Brotherhood of Steel members, as well as a Vertibird. If Duty or Dishonor has been completed by agreeing to keep quiet about Initiate Clarke, then he and Knight Sergeant Gavil will accompany the Sole Survivor in place of the unnamed knights. Also, if Paladin Brandis has been recruited back to the Brotherhood, he will fight there as well.

Eventually, Prime reaches the CIT ruins, which are guarded by a large group of synths. At this point, Elder Maxson, armed with his unique weapon, as well as more Brotherhood of Steel personnel, will join in the fight. Liberty Prime will analyze the area and detect the Institute, and proceed to use its weaponry to create an access. While it uses its eye laser and nukes to create an access, it will be unable to attack the synths, meaning that it needs to be defended by the Sole Survivor and Brotherhood personnel. After some time, Liberty Prime will throw nukes at the front of the ruins, creating a hole that will allow the Brotherhood of Steel to gain direct access to the Institute. Jump down the hole to enter the Institute, completing this quest and starting the next one, The Nuclear Option.

Quest stages

Quest stages
StageStatusDescriptionLog Entry
20 Speak to Proctor IngramIn order to get Liberty Prime's running under his own power, I should speak to Proctor Ingram.
30 Plug in Beryllium Agitator
40 Activate power transfer switchWith the Beryllium Agitator firmly in place, all that remains is pressing the Power Transfer Switch which should start up Liberty Prime's reactor.
50 Follow Liberty PrimeIt's time to take the fight to the Institute. I should escort Liberty Prime to the ruins of the C.I.T.
60 Defend Liberty PrimeI've reached the ruins of the C.I.T. I should defend Liberty Prime as he smashes his way into the Institute's underground facility.
70 Enter the InstituteLiberty Prime has successfully penetrated the Institute's defences. I should enter the Institute and begin the final phase of the attack.
255Quest finishedQuest completeThe final attack on the Institute has begun.
355Quest failedQuest failed


  • Completing Ad Victoriam while Defend the Castle is active will successfully complete Defend the Castle. However, completing Defend the Castle will automatically fail Ad Victoriam.
  • It is not required to finish Tactical Thinking to get to this quest. Just complete the quest Spoils of War.
  • During this quest, Father may appear on Diamond City Radio or Radio Freedom and tell the people of the Commonwealth that the Institute will be activating their reactor.
  • Prior to entering the tunnel into the Institute, a small number of Brotherhood of Steel soldiers will be present, alongside Maxson. They can be killed and looted without incurring any penalty whatsoever. Furthermore, a replacement will shortly appear from the east road, allowing the cycle to be repeated infinitely.
  • If Blind Betrayal has been completed and Danse has become an enemy of the Brotherhood, make sure that he is not positioned in Bunker Hill before starting this mission since this settlement is along Liberty Prime's path. If the Brotherhood attacks him, this will trigger the settlement's defenses (if set up) and will cause the settlers (or any companions stationed there) to attack the Brotherhood, leaving the player character with a stalemate Prime being unable to proceed.
  • While escorting Liberty Prime to the C.I.T. ruins, Liberty Prime is scripted to have an encounter with a behemoth, in which it effortlessly picks the behemoth up and crushes its head before throwing it away (sometimes in the water). This is scripted to happen on the bridge right before Ticonderoga safehouse.

Behind the scenes

  • Ad Victoriam is an accusative construct in Latin; ad being a preposition that is paired with an accusative, ad having the meaning 'toward', and victoriam being the accusative form of the noun Victoria, ae, a first declension feminine noun meaning 'victory', translating to: 'toward victory'.
  • Ad Victoriam is also one of the mottos of the Brotherhood of Steel, with its usage dating back as early as 2093.[1]


  • PCPC Playstation 4Playstation 4 When prompted to install the Beryllium Agitator inside Liberty Prime - the hatch is closed. Fix is unknown.[verified]
    • PCPC Open console --> Target the cover using your mouse --> enter disable --> if confronted with a reference object target that reference instead using prid "ref-number" --> enter disable again --> quit the console; the hatch is now open and one will be able to install the device properly to advance the quest. As always using the console make a fresh save before doing this steps.
  • PCPC After crossing the river and eliminating all synths, Liberty Prime may get stuck and keep throwing mini nukes on the waiting shed. One will have to fast-travel to the nearby locations like Bunker Hill or Weatherby Savings & Loan to "reload" his position.[verified]
  • PCPC When choosing to wait for Liberty Prime (i.e. sleeping or sitting and waiting) he can get stuck near Monsignor Plaza rendering him unable to continue on; attempting to fix this like the waiting shed will make the problem worse as he will then reload on the roof next to him. If one has not completed Banished from the Institute, fast travel to the Institute and finish the quest; the player character will then be transported to the C.I.T. ruins where you will fight the synths. Liberty Prime will then teleport to that location.[verified]
  • PCPC Collateral damage caused by Liberty Prime's nuke may make the settlers and traders in Bunker Hill turn hostile to him. If that happens, they will fight endlessly unless the player character wipes out the settlement, since many of the characters living there are protected from death and thus cannot be killed by Liberty Prime's attack. Reaching Bunker Hill prior to Liberty Prime's arrival and killing any and all enemies close to the settlement will prevent this.[verified]
  • PCPC Playstation 4Playstation 4 Xbox OneXbox One The enemies along the path of Liberty Prime will respawn eventually, including the synths and behemoths.[verified]