Norsca.
Under the command of the Iron Tsar, the Astartes of the Fourth Legion commenced their operations following a brief period of reorganization and the receipt of orbital resupply from the fleet stationed above the planet.
Once the Fourth Legion's signature heavy weaponry—tanks, armored vehicles, and artillery—was in position, Forrix and his subordinate commanders began their missions in accordance with the Legion's established combat style. Perturabo had demanded that the Fourth Legion deploy and fight exactly as they had done prior to his return, allowing him to better observe the operational capabilities of his gene-sons.
However, as a Primarch, Perturabo did not entirely abstain from command. He personally directed the Kislev Streltsi—the mortal army he had founded—rather than any specific unit of the Fourth Legion.
Following Kislev's integration into the Imperium as a Primarch's homeworld, the Streltsi had immediately received Imperial logistics and armaments. This ensured the Primarch's personal guard was fit for the upcoming tasks of campaigning on alien worlds.
Now, trained and equipped by the Imperium, the Kislev Streltsi had evolved into a 30th Millennium fighting force, complete with Leman Russ Battle Tanks and Basilisk self-propelled artillery.
On the planet Norsca, they were about to face their first true engagement since their reorganization.
Under Forrix's planning, the Fourth Legion Astartes began a systematic sweeping operation against the Norscan tribes. Regarding these barbarians who had slaughtered Imperial colonists, the Primarch's orders were absolute: total extermination, leaving no survivors.
While the individual combat prowess of a Norscan was formidable—enough to overwhelm the previous Governor's local militia and besiege the capital—they were little more than a disorganized rabble of sell-swords and brawlers when faced with the Emperor's Astartes.
The true strength of the Astartes compared to other augmented humans lay in their discipline.
The Emperor's refined gene-seed surgeries ensured that an Astartes gained monstrous strength while maintaining reason and order, unlike the rampaging cyborgs of Terran techno-barbarians or the frenzied thralls of technocratic tyrants.
As the Great Crusade surged out of the Sol System into the vast galaxy, the Legion's discipline and combined-arms coordination maintained a crushing advantage against the human nations left over from the Old Night.
Moreover, the Norscans lacked sophisticated technological weaponry. They possessed nothing like the ubiquitous artillery and armored divisions of the Fourth Legion. Against steel, they were merely flesh and blood.
Whenever a Norscan tribe attempted to counter-attack the "Sky-Strangers," they suffered losses beyond their comprehension.
As they charged the Fourth Legion's positions, they were met by a hail of fire meticulously planned and measured by Forrix and his officers. Countless towering Norscan men were pulverized by falling shells before they could even lay eyes upon their foes.
Those who managed to reach the Legion's lines found themselves facing a wall of mass-reactive bolts. The Astartes of the Fourth Legion ensured the barbarians were "fed" a relentless rain of fire.
Consequently, the opening encounters were not the glorious, brutal melees the Norscans envisioned. They were stories of calculated slaughter by bolter and bombardment.
The pragmatic Astartes of the Fourth preferred to watch the Norscans be torn apart by high explosives rather than "engaging cordially" with chainswords and cold steel like their cousins in other Legions.
The Norscans, however, were not fools. After several lopsided massacres, the surviving tribes realized they had to change their tactics to favor the terrain.
Unanimously, the tribes abandoned the open plains and retreated into the mountain forests where they had lived for generations. Even the dimmest warrior knew they were easily slaughtered on open ground and sought the familiarity of the heights.
The Fourth Legion easily reclaimed the plains using their preferred fire-support doctrines.
Following the Legion's victories, the Imperial colonists who had been forced into the capital returned to their abandoned settlements, re-tilling the fields and grazing their herds once more.
Simultaneously, the Fourth Legion began constructing a series of fortresses along the border of the plains and the forests to prevent further Norscan incursions.
But this was not the end of the campaign; it was merely the conclusion of a phase.
Perturabo had no intention of leaving these fickle tribes alive to betray the Imperium again. He intended to make the Norscan people history—or at least, end the existence of their tribal culture.
The retreat into the forests presented a challenge. In the uneven, densely wooded terrain, the heavy armor and artillery of the Fourth Legion could not be fully deployed.
To penetrate deep into Norscan territory, the Legion had to prepare for combat without constant fire support. To this end, Perturabo devised a new strategy.
By his order, veterans of the Fourth Legion were organized into reconnaissance units to map the Norscan tribal lands.
Using these maps, the Fourth Legion established lines of communication cutting through the barbarian regions. Fortresses were constructed at regular intervals and intersections along these routes to isolate the tribes from one another.
Under this network of roads and strongpoints, it became impossible for the Norscan tribes to support each other. The Fourth Legion and the Kislev Streltsi could then surround and annihilate these isolated pockets one by one.
It was not a "glorious" method of war, but it was highly efficient. It was exactly what Perturabo sought: the destruction of the enemy with maximum speed and minimum casualties.