The Lord Commander of the Imperium is a singular and unique military rank held by the individual who serves as the supreme commander of the Imperial armed forces and as the chairman of the Senatorum Imperialis.
Officially, the position conveys only military authority, but is usually held at the same time as the rank of Imperial Regent, which grants supreme civil authority as well, with only the Emperor of Mankind Himself ranking higher.
The position has been held only a few times in the Imperium's history, in the first case in the millennium and a half after the end of the Horus Heresy in the early 31st Millennium and most recently again after the Terran Crusade of 999.M41.
The position was first created for the Primarch Rogal Dorn, the Praetorian of Terra, who held it during the Horus Heresy so that he might coordinate the defence of Terra from the attack by the Traitor Legions of the Warmaster Horus.
After the Heresy, the office was officially added to the ranks of the Senatorum Imperialis -- the twelve most powerful individuals in the Imperium's governmental hierarchy.
He became the first lord commander of the Imperium after the Heresy, receiving the rank from Rogal Dorn so that he could stabilise the Imperium and begin the reforms of the Time of Rebirth.
He was the only man ever to command the entirety of the Imperium's armed forces after the Heresy. Before the Heresy, this function had been administered by the Terran War Council and the Imperial Warmaster.
Guilliman's directives single-handedly reshaped the Imperium, restructuring its administrative and military apparatus following the internment of the Emperor of Mankind within the Golden Throne on Terra.
Guilliman would continue to hold this title, acting as both chairman of the Senatorum Imperialis and the Imperium's military commander-in-chief, until he was fatally wounded by the Chaos-tainted blade of the Daemon Primarch Fulgrim of the Emperor's Children Traitor Legion at the Battle of Thessala in 121.M31.
The dying Guilliman was subsequently put into temporal stasis on the verge of death and his body placed upon the throne that lies in the Temple of Correction on the Ultramarines' homeworld of Macragge. The title of lord commander of the Imperium continued to be used for a time following Guilliman's internment, and the later lord commanders served as both chariman and first among equals on the Senatorum Imperialis and as the supreme commander of the Imperium's military.
In honour of the primarch, the lord commander of the Imperium was often simply referred to as "Lord Guilliman." This honorific was no longer in use by the late 41st Millennium, but is known to have been in continuous use at least until the mid-32nd Millennium.
In the aftermath of the War of the Beast and the disastrous event known as The Beheading in 626.M32, the position of lord commander of the Imperium was abolished until 999.M41, when the resurrected Roboute Guilliman returned from his millennia-long dreamless slumber on Macragge to Terra during the Terran Crusade.
Following his meeting with his father the Emperor in the Imperial Palace for the first time in ten thousand standard years, Guilliman informed the sitting High Lords of Terra that he was once more taking up the mantle of the lord commander of the Imperium.
Upon his resumption of the rank, Lord Guilliman forcibly removed several High Lords from office and replaced them with individuals of his own choosing. The resurrected primarch also warned the High Lords of an encroaching darkness, a terrible Warp phenomenon called the Great Rift that was even now manifesting itself across the galaxy from end to end.
For all the disturbing omens and disastrous losses, Guilliman urged Humanity's leaders not to give up hope. The Emperor of the Imperium was not blind to their plight, and neither was its restored lord commander.
Under Guilliman's direction, vast armies and armadas were raised in numbers not seen since the Great Crusade that had founded the Imperium ten millennia before.
- Codex: Ultramarines (2nd Edition) by Rick Priestley, pg. 8
- The Beast Arises - Book One - I Am Slaughter (Novel) by Dan Abnett, Ch. 3
- The Beast Arises - Book Twelve - The Beheading (Novel) by Guy Haley
- The Gathering Storm - Part Three - Rise of the Primarch (7th Edition), pg. 92
- Master of Mankind (Novel) by Aaron Dembski-Bowden, Ch. 3
|High Lords of Terra (Senatorum Imperialis)|
|Permanent Members||Master of the Administratum • Inquisitorial Representative • Ecclesiarch • Fabricator-General • Grand Provost Marshal • Paternoval Envoy • Master of the Astronomican • Grand Master of Assassins • Master of the Adeptus Astra Telepathica|
|Rotating Members||Lord Commander of the Segmentum Solar • Lord Commander Militant • Lord High Admiral • Cardinal(s) of the Holy Synod of Terra • Abbess Sanctorum • Captain-General • Chancellor of the Estate Imperium • Speaker for the Chartist Captains|
|Ruling Member||Lord Commander of the Imperium|