The Battle of Tallarn became the largest tank engagement ever recorded in the annals of the Imperium, a war of attrition fought across a world already murdered. When Perturabo's fleet unleashed a life-eater virus bombardment upon Tallarn, the surface was reduced to a toxic wasteland, its billions dead within hours.
Yet the Iron Warriors had not reckoned with the survivors sheltering in the deep bunkers and hive-sublevels. Emerging in sealed vehicles, the defenders waged a subterranean and surface war of armour that swelled as reinforcements poured in from across the region. For long months, countless thousands of tanks, Titans and war machines ground against one another amid the poisoned dust, visibility measured in metres, every hull a sealed coffin against the killing air.
The reasons for Perturabo's obsession with the ruined world remain debated by Imperial scholars, but the cost was beyond reckoning. The Astra Militarum forbears who crewed those machines died in their thousands, and the Iron Warriors bled for a prize that yielded little. When the guns at last fell silent, Tallarn was a graveyard of rusting steel, a monument to the industrial slaughter the Heresy had made of war.