First War for Armageddon

The First War for Armageddon is the least well known of the three Armageddon Wars, and involved the forces of Chaos and the Imperium. It was the culmination of years of preparation by the Daemon Primarch Angron, favoured of Khorne, to re-unify the World Eaters after their shattering at the hands of Khârn the Betrayer after the Battle of Skalathrax.
In the years to come, knowledge of the First War for Armageddon was suppressed by the Inquisition, to the point that even the inhabitants of Armageddon itself believe that there have been only two wars for the planet.