Gardinaal is a notable Industrial World of the Imperium of Man located near the Dominion of Storms in the Ultima Segmentum in the Eastern Fringe. Due to its people's arrogance and treachery during the Great Crusade, this world was subjected to a brutal Imperial Compliance campaign, known as the Fall of the Lords of Gardinaal, which was conducted by the Primarch Ferrus Manus and his uncompromising Iron Hands Space Marine Legion.
Following the decimation of their military forces and the death of Gardinaal's intransigent lords, the people of this world suffered both famine and great hardship, but its resources were largely left intact for Imperial exploitation. Within a few short standard years, Gardinaal and its heavy industrial output proved to be a valuable addition to the Imperium.
During the Great Crusade there were many human worlds, indeed in some cases petty interstellar empires, that resisted the Imperial Truth through fear, fanaticism or arrogance, and of these some number possessed considerable might of arms, enough to give even the Expeditionary Fleets of the Great Crusade pause. One such was Gardinaal; a stellar empire at the edge of the Dominion of Storms to the galactic east. Comprising eleven inhabited worlds, grown strong on industrial power retained through the Age of Strife and a warlike military aristocracy, it was deemed an ideal prize well-worthy of inclusion intact for the Imperium. In particular, Gardinaal's extensive and well-equipped armed forces would make ideal inductees into the ranks of the Imperial Army.
As such, negotiations for the inclusion of Gardinaal in the Imperium were deemed the first course of action, and a full delegation with an Honour Guard drawn from the Thousand Sons Legion was sent to meet with the lords of the pocket empire. At first, the talks proved promising, but soon degenerated when the Lords of Gardinaal's position became laboured and obstructive, believed to be an attempt to forestall an Imperial invasion while the Gardinaal covertly readied themselves for war. When the Thousand Sons detachment detected a psychic attempt to subvert the Imperial emissaries, they intervened, slaughtering the Gardinaal delegation, enabling the Imperial Expedition to flee, bringing news of the treacherous attack to the Imperium.
The nearby 413th Expeditionary Fleet, under the command of Master Ulan Cicerus and his XV Chapter of the Ultramarines Legion, a strong Imperial Army core of Marnean Armsmen and Serranic Peltasts and a demi-legio of the Titan Legio Atarus were dispatched to deal with Gardinaal. Initially, the Imperial forces overcame the defences of Gardinaal's outer worlds and established a blockade of the planet in space. The Ultramarines' attempt to take Gardinaal Prime with minimal collateral loss would prove disastrous, as the Gardinaal utilised powerful STC weaponry and vehicles never before seen by Imperial forces. The Ultramarines and Titans were hurled back and forced to retreat off-planet rather than fight on with no possibility of victory. Nearly half of the Titan demi-legio was lost and the Ultramarines' casualties were just as severe, but even worse, over 500,000 troops of the Imperial Army lay dead or dying on Gardinaal Prime. Repulsed and bled dry, the 413th Expedition was unable to launch another assault.
Breaking from the Warp to answer the Ultramarines' call for aid, at the head of a new war-host, Ferrus Manus led an armada comprised of both the Iron Hands and the Emperor's Children Legions. The Emperor's Children contingent led a diversionary attack, sowing panic and death across the world but leaving its infrastructure intact. Descending at the height of the diversionary attacks, the Iron Hands divided the task of taking Gardinaal Prime's main industrialised zones between the Iron Hands Clans. The assault of the X Legion was relentless and tireless, a battle fought across a thousand engagements spread over an entire world. With their domains fallen about them, the Lords of Gardinaal offered unconditional surrender to the Imperium. Ferrus Manus refused the enemy's concession and the Iron Hands led the final attack on the Gardinaal capital city. The Ultramarines, desperate to reclaim their honour from their earlier defeat, requested the honour of crossing the breach into the enemy citadel.
The Gorgon acquiesced to the Ultramarines' request, but the price the warriors of the XIII Legion paid was high, for the defenders' counterattack was powerful, sparing none of their remaining might. The world's military forces were utterly annihilated and the few remaining survivors were ruthlessly cut down, a task the Iron Hands did with cold efficiency, while the Emperor's Children Legion, circling overhead, made of it a sport. With the battle finally over, the survivors of the capital city huddled in bunkers as refugees waited in the agony of terror for what might follow. When the last of the Lords of Gardinaal had paid for their intransigence, Ferrus Manus spoke, his orders not a death sentence for the world, but of its reprieve: "It is done." The last Lords of Gardinaal had paid the ultimate price for their intransigence.
When the black-iron fleet of the X Legion left the Gardinaal System shortly afterwards, its other inhabited worlds were pleased to surrender unconditionally to the Imperium's mercy. Though initially faced with famine and hardship which blighted Gardinaal Prime for many standard years to come as the consequence of the war, the Imperial Assay found the planet's heavy industry and resources largely intact, and within a few short Terran years, Gardinaal proved a valuable addition to the Imperium and a model of Imperial Compliance.
- Ferrus Manus - The Gorgon of Medusa (Novella) by David Guymer
- The Horus Heresy - Book Two: Massacre (Forge World Series) by Alan Bligh, "Iron Hands: Exemplary Battles - The Fall of the Lords of Gardinaal," pp. 88-91