While Perturabo led the Fourth Legion on their campaign in Norsca, Kislev—his adopted homeworld and the administrative heart of his rule—underwent planned growth and transformation.
Under the governance of Perturabo Rurik Kislevsky, a Primarch of peerless intellect and absolute strength, Kislev had industrialized at a staggering pace even before the Emperor's arrival, with countless cities and factories springing from the earth.
However, after the reunion of the Iron Tsar and the Master of Mankind, the progress brought by the Imperium far exceeded what Perturabo had accomplished alone.
At Perturabo's request, the red-robed Tech-Priests of Mars organized a massive delegation to Kislev. Their mission was to instruct the people in developing their industry according to the standards of the Adeptus Mechanicus, better serving the Fourth Legion and the Great Crusade.
With them, these Martian Tech-Priests brought a monumental gift: shipyards capable of constructing Gloriana-class battleships.
Under their guidance, Kislevite workers began constructing orbital shipyards that encircled the planet's equator. Once completed, Kislev would possess the capacity to build and maintain any class of warship serving the Imperial Navy. This allowed Kislev to independently support the logistics of the Fourth Legion and the Kislev Streltsi throughout the Great Crusade.
On the surface, supported by Imperial standards and Martian technology, Kislev's major cities saw the rise of massive residential complexes known as "Hive Cities" and gargantuan factories built to Martian specifications.
As Perturabo envisioned, Kislev would become a workshop rivaling Mars or any Forge World, producing armaments for his armies day and night.
Ironically, for the former serfs of Kislev, the middle and lower levels of these planned Hives were warmer and more comfortable than their previous thatched huts. At the very least, they no longer feared the northern winds piercing their fragile homes during Kislev's merciless winters.
For the Kislevite nobles who had submitted to the Iron Tsar, Hive life had little negative impact. In fact, their standard of living in the Spire increased due to the influx of advanced technology.
Studying abroad on Terra became a popular pursuit for the Kislevite nobility. If a noble's scion lacked experience studying in core Imperial regions like Terra or Mars, the family was dismissed as "unlearned barbarians" in aristocratic salons.
To avoid family disgrace and to acquire more "civilized" knowledge, Kislevite nobles were willing to spend their fortunes sending their children to Terra. These returning youths brought Terran customs back to Kislev.
Consequently, Kislevite high society was reshaped in a short time. Old Ecclesiarchy Kislevite ceased to be the daily tongue; the new generation of nobles preferred High Gothic for communication. In the eyes of these Terranized aristocrats, Kislevite was merely a "commoner's tongue," unworthy of their personal use.
The towering Hive Cities and the vast factories controlled by the Mechanicus became the defining features of Kislev's new landscape.
This was the most visible change brought by the Imperium.
The Okhrana, Perturabo's secret police, gained Imperial technical support, making it easier to apprehend those plotting against the Iron Tsar. Whether it was a noble's secret meeting in the Spire or a commoner's association in the lower Hive, the Okhrana discovered and arrested them immediately.
In the Gulags controlled by the Okhrana, new methods were employed against recalcitrant rebels: they were handed over to the Tech-Priests to be turned into mindless servitors.
These servitors were sent to busy assembly lines or handed to the Penal Battalions as combat servitors, providing fire support. In this way, the dregs of society fulfilled a final purpose for the Tsar and the Emperor.
The Academy of Sciences, a research institution personally established by Perturabo, became an affiliate of the Adeptus Mechanicus.
Unlike the Mechanicus, however, the Kislevite Academy revered the "Cult of Perturabo." After accepting the Martian faith in the Omnissiah, these Kislevite scholars naturally viewed their mentor and founder, Perturabo, as the Agent of the Omnissiah.
During exchanges with Tech-Priests, this "heretical" belief was transmitted to the red-robed priests of Mars.
Many Martian Tech-Priests had witnessed Perturabo's miracles firsthand. The Primarch had repaired complex machines that even the most venerable Archmagi could not fix, all without prior training. This made the new faith highly persuasive to them.
As Kislev accelerated its industrialization with Martian aid, it simultaneously exported this new heresy—the "Kislevite Sect of the Adeptus Mechanicus"—back to Mars, a faith that viewed the Iron Tsar as the Omnissiah's living avatar.
Finally, and most importantly for Kislev, recruitment officers from the Fourth Legion began large-scale genetic testing of the population to determine who could undergo the augmentations to join Perturabo's Legion.
Due to the non-selective nature of Perturabo's gene-seed, nearly all Kislevite males were viable candidates for transformation into Astartes.
A new recruitment system was established: the elite recruits joined the Astartes, while the second tier entered the Streltsi.
Kislev, the homeworld of the Iron Tsar, had been transformed by the Imperium and the Mechanicus. It could now proudly declare itself ready for the Great Crusade.
This was the Kislev that Perturabo would soon lead—a world prepared for war, alongside the Fourth Legion, now renamed the "Iron Warriors."