The Imperial Aquila, known in ancient times as the Palatine Aquila, is a two-headed eagle sigil which represents the entirety of the Imperium of Man and was chosen by the Emperor of Mankind at the start of the Great Crusade in circa 800.M30. The Aquila replaced the earlier symbol of a lightning bolt that had been used to represent the Imperial forces during the Unification Wars on Terra at the end of the Age of Strife in the late 30th Millennium. The Emperor intended that the Aquila would serve as the banner under which his Space Marine Legions would forge a new galaxy-spanning galactic government for humanity. During the time of the Great Crusade before the Horus Heresy, the two-headed eagle was blind-folded on the right side, and the left side had eyes. The blind side of the symbol represented Mankind looking back into its past at the lessons of its history and traditions, while the sighted eagle was looking into the future and the hope of the better life that the Emperor would create for humanity. After the Heresy, as the Imperial Cult took hold of the minds of men, the Aquila's meaning changed to represent the political union of the Imperium of Man that had been founded on Terra between the forces of the Emperor and the Adeptus Mechanicus of Mars. Space Marines sometimes use a different version of the Aquila on their Power Armour, vehicles and weapons, which is a human skull with eagle wings on either side known as the Imperialis. This sigil is intended to represent the Space Marines' slightly different relationship with the Emperor than the rest of humanity. Traditionally, the Astartes do not believe that the Emperor is a deity but reverence him as humanity's greatest visionary and for the extraordinary sacrifice he made for the sake of Mankind when he defeated Horus and allowed himself to be interred as a living corpse within the Golden Throne. The Astartes are willing to defend the Emperor's original conception of the Imperium to their last breath despite his current existence trapped somewhere between life and death.
Sign of the Aquila
The Sign of the Aquila is a universal hand gesture used to show one's allegiance to the Imperium of Man, and is known to every citizen within its boundaries. It is used as a respectfully neutral greeting or farewell gesture, mainly when one is unsure of the recipient's rank and/or the proper etiquette in the given situation. There is some debate as to how the gesture is made: the Sign of the Aquila has its user place their hands flat on their chest with their thumbs interlocked. This forms the image of the Imperial Eagle on the chest with the thumbs forming the heads and the straight fingers symbolising its wings. The Aquila gesture is often accompanied by a nod or slight bow.
The Aquila is also displayed on Space Marine Power Armour since the end of the Horus Heresy when that honour was given to all Loyalist Space Marines by the Emperor rather than just the Traitor Marines of the Emperor's Children Legion. The Aquila is also stamped on weapons produced for the Imperium at its Adeptus Mechanicus Forge Worlds. Bolters, Lasguns, tanks, and every other piece of Imperial military equipment often displays the Aquila painted or stamped on them. The Aquila is also stamped on signet rings belonging to those serving in an Imperial office, in the Imperial military or in another Adepta of the Adeptus Terra like the Administratum.
- Codex: Imperial Guard (3rd Edition, 2nd Codex)
- Imperial Armour - Volume Two - Space Marines and Forces of the Inquisition - First Edition (Forge World), pg. 247
- Warhammer 40,000 Rulebook (5th Edition)
- The Flight of the Eisenstein (Novel) by James Swallow