Istvaan V

Istvaan V was where the Legions of Warmaster Horus redeployed following the virus-bombing of Istvaan III. Upon learning of the terrible atrocity Horus had committed, the Emperor deployed seven Legions to bring Horus to account for his actions. The Iron Hands, Salamanders and Raven Guard made up the first wave of the attack, but were pushed back by the superior tactics of Horus' maddened followers. The reserves were called in, but the four Legions comprising the reinforcements - the Iron Warriors, the Alpha Legion, the Word Bearers and the Night Lords - had betrayed the Emperor and were prepared to follow Horus. The three loyalist Legions were almost annihilated.