The specialized Imperial Guard regiments recruited from the Fortress world of Galcrezia. Collectively known as Galcrezian Exterminator regiments, they have a long and illustrious combat record. In particular these regiments specialize in dealing with "Horde Xenos", otherise known as Orks and Tyranids.
The planet Galcrezia was colonised some time in M33. At first it was a small colony, but eventually it grewto a large settlement. It was part of a small, and particularly unimpressive sector named the Voh sector located in the Ultima Segmentum. It served primarily as the headquarters for the merchant guilds within the sector.
However this would all change in M35. Two millenia after it was founded the planet came under attack with the rest of the sector by Ork forces. The sector had been unfortunate as it came into the path of Waaagh! Blasgutz. Up until then the entire sector had gone largely unmolested, as it was small and had little to offer would-be attackers. The sector was unprepared for such a furious assualt.
Despite being caught flat-footed galcrezia and numerous other planets rallied to fight the Orks. Galcrezia itself was attacked by Blasgutz personal warband. The inexperianced PDF was being dominated at first, but thanks to the military skills of the legendary General Klove, the PDF was able to hold it's own against the Ork invaders. With General Klove besting Blasgutz forces. This along with the arival of Imperial reinforcements forced the Orks to retreat, ending the rampage of Waaagh! Blasgutz.
However their trials would not be done. Waaagh! Blasgutz would settle, and put down it's roots to create an Ork Empire. Unfortunately this empire would be very close, with Galcrezia not far from the edge of it's borders. Fearing that the empire would attack again, and impressed with the skills of galcrezia's PDF, the Deparmento Munitorum decided to garrison Galcrezia, turining it into a Fortress world.
Over the years the planet, and the surrounding systems would be attacked by Orks regularly. As such the PDF and Imperial Guard regiments of Galcrezia would become adept at fighting the Green Tide, and join the ranks of the Armageddon Steel Legion and Valhalla Ice Warrior as some of the best Ork fighters in the Imperium.
Galcrezia would continue to perform it's duties, primarily fighting against the Orks. Thay is until they found a new enemy worthy of their skills. In 746.M41 Galcrezia would nearly be destroyed by one of the Imperium's newest enemies, the Tyranids. The planet was unfortunately in the path of a tendril of Hive Fleet Behemoth.
Like the rest of the galaxy at the time, Galcrezia was not prepared for this formidable foe. The Orbital Defenses were more or less destroyed outright. The Tyranids rained Myotic Spores all over the planet. The PDF did it's best to fight back, but could not handle the swarms of genetically engineered monsters that were swarming over their defences. The outsome looked bleak.
Even thought they were being beaten terribly, the Galcrezian forces still had hope. In a manner that mirrored General Klove before him, a member of the PDF named Colonel Vance Drike managed to rally the beleagured defenders. He reorganized the forces and made a counter-attack. His leadership allwed the PDF to hold out against the onslaught of the Tyranids. The regiments that came from the planet cmae back, and with frsh troops they drove the Tyranids off.
The regiments would be redeployed in order to support other worlds that were under attack. This caused a military renaissance among these regiments, who became just as adept at fighting Tyranids as they were at fighting Orks. The Galcrezian Exterminators would participate in every major conflict between the Imperium and the Tyranids since.
Since the regiments of the Galcrezian Exterminators tend to be very specialized towards battling Ork and Tyranids they tend to have a similar organization, and sense of battle style. Due to the fact that they tend to fight enemies that come in large numbers the regiments tend to be on the larger size. This becomes important as they need to rotate their soldiers in order to prevent fatigue whiule fighting the countless waves of enemies.
The command structure of the regiments tend to be very flexible and effective. Colonels and Captains are taught how to utilise the specialties, and movements of the units under their command in order to maximise the efficiency of the fighting force as a whole, with the actions of each unit, be they squad or company, complimenting those of the others. The actions are so well coordinated that other Imperial commanders often note that it seems like hte regiment itself has a Hive Mind. Lower level officers are not helpless without their commanders though. They are taught survival skills, and to take the initiative in battle. This means that the regiments can fight effectively even in the event that they are cut off from central command.
In battle the regiments tend to focus on firepower. They make extensive use of tanks and heavy weaponry, employing anti-horde tactics in order to combat their opponents, which tend to be numerically superior. They also make liberal use of Biological and Chemical warfare in order o gain the edge on the Orks and Tyranids.
Finally the regiments tend to be better at Close Quarters Combat than is usual for the Imperial Guard. The regiments are constantly requesting Ogryn auxilliaries, which they use in order to counter the Orks and Tyranids, both enemies that tend to be more dangerous up close.
Furthermore nearly every regiment keeps a force of CQC Veterans. These are a set of extremely Choppy individuals that the regiments train to fight the enemy up close and personal. They are some of the best close quarters fighters in the Imperial Guard, with skills in that branch of combat rarely seen outside of Space Marines.
While the regiments are impressive, they are not without weaknesses. Due to their methods of fighting these regiments tend to be lacking in Fast Attack options, meaning they tend to be slow moving. Also due to the fact that they are focused on Anti-Ork and Anti-Tyranid warfare, they tend to be less successful against opponents like Tau, Necrons and Eldar.
Finally they are a better force when it comes to defensive warfare than they are on the offense. This is not to say that they are incapable of launching an attack. They are good on the attack, but they truly shine on the defensive, prefering to weather whatever their opponents can throw at them while waiting for them to weaken, and then launching a counter-attack.
- "Well you've done it. You bought literally all the Promethium I had warehoused in this sector, I guess that means Ork-flambe is on the menu? Have fun!"