Rogal Dorn - The Iron Cage: The battle known only as the Iron Cage has gone down in history as one of great tragedy and remorse for the Imperial Fists. However, some suspect that Dorn already knew the outcome when he threw himself and his Legion into the assault. It is believed Dorn knew that many of his zealous warriors would never accept the dissolution of the Legion as the adoption of the Codex Astartes required, and that by throwing themselves into the suicidal assault on the Iron Cage they would at least be granted an honourable death, for that is exactly what many of them got.The Iron Cage was actually a defensive trap set by the Iron Warriors Traitor Legion on the world of Sebastus IV, that was known as the Eternal Fortress, and which was a besieging force's nightmare straight from the depths of hell.The Iron Warriors were masters of siege and defence and Perturabo's writings on the subject had even been retained by the Primarch Roboute Guilliman in the Codex Astartes. But Dorn was Perturabo's equal, and furious at the defiance of the Traitors, the Imperial Fists launched an all-out assault straight into the heart of the Iron Warriors defenses within the Eternal Fortress, enraged that the enemy had dared raise their heretical banners over another Imperial world.Without any planning or strategy the Fists fought with zeal, endurance, and sheer grit determination, breaking out of every trap, fighting through every ambush and breaching every defense that got in their way. Dorn led the attack, a colossus who threw back every assault. While the battle should have favored the Iron Warriors in their network of trenches and redoubts the Imperial Fists matched the Iron Warriors guile with cold fury. Brother fought brother in half flooded trenches, tearing at each other with knives and chainswords when all ammunition was expended, neither giving nor expecting any quarter.The Iron Warriors' Daemon Primarch Perturabo had built the massive fortifications to mock the Imperial Fists, and Dorn led his most die-hard followers in a siege that would last for several weeks. The Iron Warriors, now twisted Chaos Space Marines, claim that the Imperial Fists suffered a crushing defeat, and that Dorn and his Legion would have been wiped out if Perturabo hadn't prolonged Dorn's suffering so long that the Ultramarines managed to intervene. Imperial records of the battle indicate otherwise. The Imperial Fists had always been masters of siege craft, and even unprepared and at a disadvantage they fought like lions. Dorn stood as a giant in their midst, his mind clear with purpose after years of doubt and guilt.Eventually it became obvious that though the Imperial Fists had suffered horrible losses, the Iron Warriors could not finish them off, lacking the faith to make the ultimate sacrifice to achieve victory. During a pause in the fighting Roboute Guilliman and his Ultramarines intervened in the struggle, extracting the battered Imperial Fists and letting the Iron Warriors escape.Guilliman had decided that the destruction of the Iron Warriors was not worth the death of Rogal Dorn and so he came with the entirety of his Ultramarines to break up the brutal fight and drive the Iron Warriors off. With their cleansing in the fires of battle at the Iron Cage over, the Imperial Fists withdrew into seclusion, letting their successor Chapters take to the field in their stead. For two solar decades the Imperial Fists re-organised. Under the direction of Dorn, the Chapter absorbed the tenets of the Codex Astartes and by the time they reappeared on the battlefields of the Imperium their adherence to the Codex was second only to the Ultramarines themselves.