Iron Crusade

The Iron Crusade was an Imperial castigation campaign carried out by the Sons of Iron Space Marine Chapter against the various enemies of Mankind within the Imperium Nihilus, the region of the galaxy cut off by the galaxy-wide tear in reality, known as the Cicatrix Maledictum, that formed after the fall of Cadia during the 13th Black Crusade.

Background
Once the second Inflexible had cemented his position and nursed some strength back to his Chapter, he gathered the full might of the Sons of Iron, save a Squad from each Company but the First and Second, remaining on Suami, and declared a Crusade against all foes in the Imperium Nihilus. During almost sixty years, the Sons brought backworlds lost to the Xenos, Chaos Cultists and even debased secessionists. Tuomas Vahanen gathered all the forces he could muster, Astartes, Primaris or Astra Militarum, including the famous 215th regiment from Suami, among many other forces hailing from the ravaged world. Even as losses mounted, Vahanen refused to call off the Crusade and it was only when the Sons and their allies had spent the last ten years besieging the Hive-World of Corona Gloria Mundi, near Sable, that he admitted that the Iron Crusade couldn't last longer. Less than five hundred Brothers remained. Since that time, all new aspirants have been made into Primaris at the express order of the Second Inflexible.