The Drop Site Massacre

When the Emperor learned that his beloved Warmaster had turned against him, he despatched seven Legions to bring Horus to heel. What awaited them on the black sands of Isstvan V became The Drop Site Massacre, the most infamous treachery of the Age of Darkness and a wound from which three proud Legions never recovered.

The assault was launched in waves. The first to make planetfall were the Iron Hands, Salamanders and Raven Guard, who drove hard into the traitor lines while four further Legions (Alpha Legion, Iron Warriors, Night Lords and Word Bearers) held the high ground behind them as the second wave and reserve. It was a trap years in the making. As the loyalists closed with Horus's warriors and pressed for a decisive breakthrough, the reserve Legions levelled their weapons and opened fire into the backs of their own brothers.

Caught between two hosts with nowhere to run, the loyalist assault disintegrated into a killing field. Ferrus Manus, primarch of the Iron Hands, was run down and beheaded by his once-brother Fulgrim, and his Legion was all but annihilated in an instant of grief and fury. Vulkan and Corax were lost amid the carnage, their Legions shattered, the scattered survivors fleeing into the dark to wage a broken and vengeful war. Of the tens of thousands who had made planetfall, only a maimed remnant clawed their way off-world.

The massacre handed Horus the momentum he needed to march on Terra, yet it also forged an undying hatred. The crippled survivors banded together as the Shattered Legions and hounded the traitors for the remainder of the war, striking from the shadows wherever they could. The full horror is recounted in the chronicle of the Drop Site Massacre.