Event · M31
Drop Site Massacre aftermath
The Drop Site Massacre aftermath denotes the events that followed Horus’s ambush of loyalist Space Marine Legions on Isstvan V in 007.M31. Having already tested loyalist resolve at Isstvan III, Horus summoned the Raven Guard, Salamanders, and Iron Hands to the same system under the pretence of a continuing campaign, then turned the World Eaters, Emperor’s Children, Death Guard, Sons of Horus, Night Lords, Word Bearers, and Alpha Legion against them on the drop sites below. The three loyalist Legions, unprepared for betrayal on this scale, suffered catastrophic losses in a single engagement that reduced their fighting strength for the remainder of the war. Amid the slaughter, the Iron Hands primarch Ferrus Manus was killed in single combat by Fulgrim of the Emperor’s Children, a death that hardened his Legion’s survivors into a grim and unforgiving temperament thereafter. Corvus Corax of the Raven Guard and Vulkan of the Salamanders, both grievously reduced in strength, fought clear of the drop sites and led remnants of the three Legions off-world through a contested void engagement, escaping annihilation but not the scale of the loss. In the aftermath, survivors of the three broken Legions dispersed across the war-torn regions of the Isstvan system and beyond, fighting on in small, self-directed formations later remembered as the Shattered Legions, harrying traitor supply lines and holdings rather than mustering as intact forces. The massacre confirmed to loyalist commanders that Horus’s rebellion was no localised mutiny but a galaxy-spanning civil war, hardening resistance that would carry through to the Siege of Terra in 014.M31, and it stands alongside the Istvaan III Atrocity as the defining opening betrayal of the Horus Heresy.
See where Drop Site Massacre aftermath occurred on the galactic map during the Horus Heresy.