The Last Wall, also called the Last Wall Protocol, was a secret stratagem of the Imperial Fists Space Marine Chapter that called for all the Successor Chapters of the Imperial Fists Space Marine Legion to reunite in the event that Terra itself came under grave threat.
The protocol was enacted during the War of the Beast in 544-546.M32.
Following the adoption of the Codex Astartes in the early decades of the 31st Millennium, the ancient Space Marine Legions were divided up into one thousand separate Chapters. These smaller forces were created so that no single commander could ever again deploy the full power of a Space Marine Legion as had happened during the Horus Heresy.
During this time, the Imperial Fists Primarch Rogal Dorn secretly laid the foundations for the emergency protocol known as the Last Wall. It was a contingency plan intended to be used only if the Imperium was ever brought to the brink of annihilation as had happened during the Heresy.
The Last Wall Protocol was laid down by Rogal Dorn in secret, in direct contravention of the proscribed dictates of the Codex Astartes and the oaths sworn after the Heresy when Roboute Guilliman's reforms of the Imperium were enacted. The Last Wall Protocol could result in the condemnation of those who dared follow its dictates as Traitors to the Imperium.
The Last Wall was only to be enacted in the event that Terra should face a grave threat, or perhaps even have fallen to an unknown foe. Then the sons of Dorn would come together to deal with the matter, reforging the VII Legion of old. Though the Space Marine Legions had been broken apart by Imperial decree, the Imperial Fists' Successor Chapters would remember, and come together in the last place their enemies would ever look for them. A place that lived long in the memory of Rogal Dorn's sons -- the Phall System.
The protocol was activated during the War of the Beast in 544.M32, which saw the galaxy invaded by an Ork WAAAGH! that rampaged across the Imperium on an unfathomable scale. The number of attacks grew until it became the greatest Greenskin invasion that the galaxy had ever known, eclipsing even that defeated by the Primarch Horus Lupercal upon the world of Ullanor in 000.M31 during the final years of the Great Crusade. At the appointed time, the Imperial Fists, Black Templars, Crimson Fists, Excoriators, Iron Knights, Fists Exemplar, and Soul Drinkers all gathered in the Phall System.
The activation of the protocol was considered controversial at the time even amongst the Imperial Fists Successor Chapters. Black Templars High Marshal Bohemond made his displeasure known when it was enacted by the Imperial Fists' Chapter Master Koorland, the "Last Son of Dorn." He obeyed the formal summons only reluctantly. Bohemond felt that his Chapter's first duty should be to the continuation of their never-ending, galaxy-wide Imperial Crusade against the enemies of Mankind, as dictated by his Chapter's founder, Sigismund.
Likewise, Acting First Captain Zerberyn of the Fists Exemplar abhorred the Last Wall Protocol. It was his Chapter's founder, Oriax Dantalion, who had convinced Rogal Dorn of the wisdom of adopting the Codex Astartes and allowing for the division of the VII Legion into separate Chapters.
Despite their misgivings, all the scions of Dorn understood that the War of the Beast represented the dire situation for which their Primarch had created the protocol. The Imperium was beset by a foe likely to triumph over all other Imperial forces. No single Astartes Chapter could stand against this menace, so the bonds of the old Legion had to be joined again.
The so-called "Last Wall" Chapters suffered heavy casualties during the prosecution of the War of the Beast. However, each donated a portion of their strength to help rebuild the Imperial Fists Chapter after it had been destroyed on the world of Ardamantua before the start of the conflict. The War of the Beast currently represents the only time the Imperial Fists Successor Chapters have enacted the Last Wall Protocol.
- The Emperor Expects - The Beast Arises, Book 3 (Novel) by Gav Thorpe
- Throneworld - The Beast Arises, Book 5 (Novel) by Guy Haley
- Echoes of the Long War - The Beast Arises, Book 6 (Novel) by David Guymer
- Shadow of Ullanor - The Beast Arises, Book 11 (Novel) by Rob Sanders