The Iron Blood is notable for taking part in the Battle of Phall, a major void engagement that took place following the start of the Horus Heresy in the early 31st Millennium after the Istvaan III Atrocity, between the entirety of the Iron Warriors Legion's fleet and a formidable Imperial Fists Legion Retribution Fleet. Perturabo was sent by the Warmaster Horus to halt the encroaching Imperial Fists fleet that had originally been sent to Istvaan III by their Primarch Rogal Dorn to reinforce the beleaguered Loyalists trapped on that world. The Traitors could not allow such a strong complement of Astartes to infiltrate their controlled area of space, for the Loyalists' presence would seriously disrupt preparations for the Traitors' drive on Terra. Commanding the entirety of his Legion's war