Event · M31

First Siege of Hydra Cordatus

The First Siege of Hydra Cordatus was an Iron Warriors assault of the Horus Heresy, fought around 007.M31 against the Imperial Fists garrison of Hydra Cordatus and led in person by Perturabo, primarch of the Iron Warriors. It is distinct from the later siege of the same world by Iron Warriors forces in the forty-first millennium. The Imperial Fists had brought Hydra Cordatus to compliance during the Great Crusade, and Rogal Dorn had left Captain Felix Cassander of the 42nd Company with two hundred legionaries to garrison the Cadmean Citadel, an ancient fortress of unknown origin able to repair damage to its own walls. Recalled to Terra, the garrison was stranded when its Navigator died, and learned of Horus’s rebellion before a replacement could be found. The Iron Warriors opened the attack with a magma-bomb bombardment of the surrounding valley before landing legionaries, guns and siege equipment for a formal investment, with Forrix and Harkor among the Triarchs directing the works. Perturabo himself spoke to few of his commanders, issuing his will through Soltarn Vull Bronn, known as the Stonewrought. Over three months the defenders, who sheltered tens of thousands of civilians within the citadel and fought alongside Mechanicum and Solar Auxilia troops, lost three-quarters of their legionaries. In the final assault Kroeger scaled the northern wall and shot Cassander, after which Perturabo landed atop the fortress by Stormbird with his Iron Circle bodyguard and broke the remaining defenders. Most of the Imperial Fists were killed, Cassander was taken prisoner, and the human refugees were slaughtered or enslaved, leaving Hydra Cordatus a barren wasteland. Fulgrim joined Perturabo on the world after its fall and drew him into the expedition that ended on Iydris.

See where First Siege of Hydra Cordatus occurred on the galactic map during the Horus Heresy.

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