"Some may question your right to destroy ten billion people. Those who understand know that you have no right to let them live."
- — Exterminatus Extremis
Exterminatus is the name of a terrible order in High Gothic given by the highest authorities of the Imperium of Man to destroy an entire planetary biosphere and all life upon a world. This action is only taken in those extreme circumstances where a potential or actual extinction-level strategic threat to the entire Imperium exists on the planet and might spread to other Imperial worlds.
Exterminatus is typically only used as a last resort, when the price of holding or retaking the world for the Emperor is deemed too high, or the threat of mutation, disease or Chaos heresy spreading to the rest of the Imperium is too great to contain by conventional means.
Thus Exterminatus has very rarely been used on vital or strategically valuable planets to the Imperium. Typically, the order may only be given by a high-ranking Imperial commander in the Astra Militarum, Imperial Navy or the Adeptus Astartes, or by a full member of the Imperial Inquisition. An Exterminatus action can be carried out in many different ways, as outlined below.
"There is no place for the weak-willed or hesitant. Only by firm action and resolute faith will mankind survive. No sacrifice is too great. No treachery too small."
- — Liber Doctrina Ordo Hereticus, Chapter XXVIII, "Exterminatus"
Note that with the exception of those methods listed under the section Other, the rest of the weapons described here are deployed from warships in orbital space.
An orbital bombardment from Imperial warships is the simplest means of carrying out an Exterminatus, as it can be done solely through the conventional firepower already available to the Imperial Navy. The power of an orbital bombardment can range from small precision strikes, not unlike that of modern surface-to-surface missiles, to the unleashing of full thermonuclear blasts.
Typically, specialised munitions like Cyclonic Torpedoes (see below) are used, designed to destroy all life on a planet's surface and potentially any entrenched even in the planet's crust.
Imperial Virus Bombs release a special pathogen known as the Life-Eater Virus that was genetically designed to quickly spread and destroy all organic cellular structures it infects, reducing all planetary life, whether flora or fauna, to an undifferentiated organic sludge of biochemicals and organic gasses as a by-product, both of which are highly flammable.
Exterminatus protocols dictate that a lance strike or an incendiary device be deployed to ignite the byproducts and turn the atmosphere into a firestorm that usually takes out whatever life may be left. Only those who may have escaped into especially-deep underground shelters can survive a Virus Bomb attack. The population of Tallarn managed to escape complete destruction this way, but their once-verdant world was forever transformed into a desert.
Virus bombs are known for their extreme speed; during the Horus Heresy, they completely wiped out Istvaan III's entire population of 16 billion people in only solar minutes, leaving the planet barren but habitable, if only just; Space Marines on the ground had to act quickly to create desperately improvised air-proof shelters. While many Astartes survived, the toll, even on many of those who had thought they were safe, proved catastrophic.
A Cyclonic Torpedo is an Imperial weapon of mass destruction that is deployed from a voidcraft into low planetary orbit. There are a wide variant of weapon types covered under the designation of Cyclonic Torpedo, including the Atmospheric Incinerator Torpedo, but all possess the capability to destroy the entire biosphere of the target world, either through the initiation of a thermonuclear reaction that ignites all free oxygen in the atmosphere or the simple expedient of nuclear-fusion-assisted plasma bombardment.
Whatever the exact origin of the mass death to come, the result of these weapons is always the same: the complete destruction of the planetary biosphere, its atmosphere burned away into the void and its oceans boiled to vapor, leaving behind the barren bedrock of a Dead World.
The blast radius is large enough to be seen from space and the detonation usually powerful enough to crack a planet's crust and destabilise its core. The Cyclonic Torpedo is only used by the armed forces of the Imperium of Man to carry out an authorised Exterminatus action on a world that has been deemed to present a strategic extinction-level threat to other inhabited regions of the human-settled galaxy.
The only organisations known within the Imperium to have access to and to have ordered the use of Cyclonic Torpedoes to carry out an Exterminatus are the Inquisition and the Adeptus Astartes. An Inquisitor has the absolute authority to order an Exterminatus action at any time, and a number of Chapter Masters of the Adeptus Astartes have carried out such regrettable actions under their own authority.
The sacrifice of an entire world and potentially billions of lives is no easy matter for even the often-callous Inquisition; an Inquisitor who orders such an extreme action will have his course closely scrutinised by his fellow Inquisitors. If they deem his decision to have been unnecessary, he may very well find himself declared a Heretic and hunted down.
Two-Stage Cyclonic Torpedoes
Two-Stage Cyclonic Torpedoes, which are a more exotic form of the standard Cyclonic Torpedoes, are the most common of a special class of rare Exterminatus weapons, designed for use against atmosphere-less or biologically-void worlds (Necron Tomb Worlds being the main example).
These torpedoes possess two-stage warheads: The first stage is an unusually powerful Melta Charge that bores straight through a planet's crust and mantle all the way down to its core.
The second stage is a modified Cyclonic Plasma Charge that destabilises the core, in most cases physically destroying the planet from the inside out.
During the conquest of the world of Loki, Lord Commander Solar Macharius ordered the destruction of the entire world. Macharius instructed the Tech-priests to change the orbit of Loki's moon, which was achieved by using huge machines placed on the surface that would use massive plasma drives to reposition the moon into the correct orbital path.
The result of the impact was not total planetary destruction, but ended up causing massive shockwaves across the planet, which resulted in massive earthquakes and waves of lava to spill out of the planetary crust. In the end, the only people to survive the destruction, were heretics held up in massive fortresses.
Recently, during the 13th Black Crusade of 999.M41, Lord Castellan Ursarkar E. Creed, the Planetary Governor of Cadia and Imperial Commander of the entire Cadian Sector of the Segmentum Obscurus, ordered a massive nuclear fusion Plasma Reactor (Generatorium), on the prison world of St. Josmane's Hope to be overloaded when it seemed that Chaos would finally take the world.
Rather than a colossal meltdown, the reactor exploded with furious energy and blew the entire planet apart with the force of its blast.
- Warhammer 40,000: Rulebook (6th Edition), pg. 154
- Horus Heresy Series (Novels)
- Ultramarines Series (Novels) by Graham McNeill
- Inquisition War Trilogy (Novels) by Ian Watson
- Fall of Macharius (Novel) by William King, pp. 215- 217
- Dawn of War II (PC Game)
- Dawn of War II - Retribution (PC Game)
- Warhammer 40,000: Fire Warrior (Video Game) (Campaign Ending Cutscene)