The Armageddon Wars were a series of three major conflicts fought during M41 on the Imperial Hive World of Armageddon. Because of the planet's vital strategic and economic importance to the rest of the Imperium, it has presented an inviting target to numerous enemies, and, for the same reasons, has been defended just as fiercely.
- The First War for Armageddon (441 M41): The forces of Chaos, led by the World Eaters Chaos Space Marines and their Daemon Primarch, Angron, invade Armageddon, and are narrowly defeated by a combined force of the PDF, the Imperial Guard, the Space Wolves, and the Grey Knights. The victory is a hollow one, after the Administratum and the Inquisition declare the human defenders of Armageddon tainted for being exposed to Chaos. Armageddon being too important to be subjected to Exterminatus, these defenders are instead sterilized and hidden away in slave labor camps, and public knowledge of the War is ruthlessly suppressed.
- The Second War for Armageddon (941 M41): A massive Ork Waaagh!, led by Warboss Ghazghkull Mag Uruk Thraka invades Armageddon. Because of the ineptitude of Overlord Herman von Strab, much of the planet's military resources are squandered and the Orks steadily gain ground, until they are halted at Hades Hive by a ferocious defense led by Commissar Yarrick. The Orks fail to overrun the planet before the Blood Angels Space Marines arrive and launch a counter-offensive that drives them off-planet.
- The Third War for Armageddon (998 M41): Ghazghkull Thraka re-invades Armageddon after decades of planning and preparation, with an even greater-sized Waaagh! Commissar Yarrick is appointed supreme commander of the defending Imperial forces. With his leadership, a combined force of PDF, Imperial Guard regiments, and Space Marines from more than twenty chapters manage to reduce the combat to attrition, with neither side achieving a decisive advantage. Ghazghkull eventually grows tired of the stalemate and withdraws, while Yarrick and the Black Templars follow in pursuit, determined to rid the galaxy of Ghazghkull for good.