Event · M31

Battle of Tallarn

The Battle of Tallarn was a campaign of the Horus Heresy fought on the Imperial world of Tallarn against the Iron Warriors Traitor Legion. Taking place during the thirty-first millennium, in the period after Warmaster Horus turned against the Emperor, it is recorded as the largest armoured engagement in Imperial history, fought across the planet’s surface between the invading Iron Warriors and a vast number of Imperial Army tank regiments. The Iron Warriors, having joined Horus’s rebellion, arrived at Tallarn after fleeing the Eye of Terror, where their erstwhile allies the Emperor’s Children under Fulgrim had abandoned them to the destruction of the world of Iydris. The disordered translation out of the warp brought the fleet of the primarch Perturabo, aboard his flagship Iron Blood, unexpectedly close to the Tallarn system. Tallarn itself, a former hub of the Great Crusade still equipped with extensive underground armouries and shelters, possessed only neglected orbital defences and had little warning of the attack. On Perturabo’s order, the Iron Warriors fleet unleashed virus bombs upon Tallarn before any ground assault began, seeding the atmosphere with the Life-eater Virus and killing the greater part of the surface population within hours. Believing the world cleared of defenders, the Iron Warriors descended to occupy it, but a large portion of the population, together with numerous Imperial Army armoured regiments under Governor-Militant Dellasarius, had survived in subterranean shelters built during the Great Crusade. Emerging in sealed vehicles to withstand the poisoned atmosphere, these forces met the Iron Warriors, reinforced in time by Mechanicum war engines and Titan Legios loyal to the Throne, in a protracted armoured struggle across the ruined surface. Losses were heavy on both sides, and loyalist commanders including Marshal Lycus were among the dead, before further reinforcements arrived and forced the Iron Warriors to withdraw. The fighting left Tallarn’s biosphere destroyed, its oceans and forests replaced by a toxic desert that persisted for generations, though the world remained in Imperial hands. From among its survivors arose the Tallarn regiments of the Imperial Army, whose descendants, the Tallarn Desert Raiders, became noted for the mobile, hit-and-run armoured tactics their forebears first practised amid the ruins. Fought within the wider Horus Heresy, the Battle of Tallarn is recorded as one of the costliest engagements of the war for both the traitor and loyalist forces involved. Perturabo’s purpose at Tallarn is recorded as the recovery of the Black Oculus, also called the Cursus of Alganar, an ancient warp portal buried beneath the planet. He withdrew into his workshop aboard the Iron Blood while Forrix held acting command, then emerged to direct a renewed assault on the Northern Desolation and the Sapphire City under Warsmith Cyrus Strux. Horus’s emissary Argonis, investigating the campaign with the help of Alpha Legion agents, confronted Perturabo aboard the Iron Blood, where an image of Horus manifested through the altered astropath Prophesius and ordered the primarch to kneel and abandon the campaign. The Contemptor Dreadnought Hrend, sent to the portal, destroyed himself rather than yield to the daemonic power within, burying the Black Oculus. Accounts thus attribute the Iron Warriors’ withdrawal both to the arrival of loyalist reinforcements and to the Warmaster’s command, and the Legion’s losses obliged Perturabo to order a mass recruitment.

See where Battle of Tallarn occurred on the galactic map during the Horus Heresy.

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