The question of where the Astartes had gone could, in fact, be explained in two words: base-swap.
Yes, if the Tyranids could use high-value units to headhunt human leaders, why couldn't humanity reciprocate and take the Tyranid leaders' heads?
Moreover, the officers and soldiers of the Helldivers looked virtually identical, making them incredibly difficult to distinguish.
In contrast, a Tyranid Synapse Creature was invariably the largest and most dramatically shaped entity on the battlefield—targeting it was a sure bet.
From the moment of their creation, the Astartes were intended to be the elite scalpel of the Imperium.
Since the Horus Heresy, the colossal Space Marine Legions had been reformed into Chapters, each limited to a thousand warriors. Their expertise lies in specialized missions like headhunting and deep-strike disruption.
To have them fight a static trench war against millions of enemies? Unless it was a Chapter specifically known for such tactics, wouldn't that just be pure idiocy?
They naturally had to leverage the Astartes' superior mobility and formidable individual combat power. Having them squat in trenches alongside the Helldivers would be a massive waste of their effectiveness.
Furthermore, it's not as if they would gain any particular advantage in the defensive line—given their abnormal, towering physique, engaging the Tyranids from the relatively narrow confines of the trenches would surely make them easy-to-hit targets for a swarm that currently prioritized long-range firepower, turning them into targets to be spun like tops.
While the Ceramite Power Armor worn by the Astartes was far more resistant to damage than the bugs' chitinous armor, who would intentionally take a hit just because they were wearing a bulletproof vest?
Perhaps many Helldivers would, but the Astartes here were clearly not Cadians by origin, and their gene-seed stemmed from Guilliman, not Fulgrim; they did not harbor a masochistic desire to be shot.
At this moment, a dozen Space Marines were silently infiltrating the deep purple spore-mist, their Power Armor's servo-systems adjusted to silent mode, making them almost one with the environment.
"The Helldivers' position is under heavy fire," whispered Reinhard through his helmet's internal comms channel. The explosions and shrieks coming from the distance were clearly audible, even several kilometers away.
"Focus on the mission, Brother Reinhard," the Ultramarines Sergeant leading the squad replied sternly, his tone steady and firm.
The Sergeant clearly had great confidence in the Helldivers, harboring no concern that the position might fall without them, leaving his own squad without a retreat path.
This was normal; in his view, the Helldivers had held out for so long with only primitive defenses. Now that they had switched to a new position with terrain and fortifications several times better than the last, how could they possibly fail to hold?
Moreover, he had personally witnessed the insane resilience of this mortal force in previous battles. They treated death as a usable resource—building walls with their corpses, trading their lives for the lives of the bugs. He had complete faith in such a troop.
And his willingness to lead these Battle-Brothers from different Chapters on a headhunting mission in such low visibility was naturally also rooted in profound self-assurance. Had he not possessed it, he would never have convinced these Space Marines from different Chapters.
Where did this confidence come from? It was simple: the Tyranids' ranged units were shelling the area relentlessly, which meant there must be a high-ranking Synapse Creature orchestrating the attack from the rear.
All they had to do was follow the sound of the bombardment and eliminate that thing.
It was a very simple plan, and not a single Space Marine raised an objection. On a rapidly changing battlefield, variables are endless; the simpler and clearer the plan, the better.
If one insists on hatching complex, multi-layered schemes to prove their unparalleled intelligence... their fate would likely resemble that of Tzeentch, whose so-called grand plans almost always went awry, forcing him to stubbornly declare, "Just as planned," in the end.
His only truly successful scheme was perhaps instigating Magnus to shatter the Webway... but in all fairness, that plan was clearly not that complicated either.
And while I have been rambling to you, the Astartes have quietly bypassed the Tyranid charging forces and arrived at a stretch of biologically engineered ground.
Giant, tumor-like Bio-Artillery pieces were deeply rooted in the earth, each pulse spraying deadly acidic spores. And in the center of these behemoths of war, they successfully located the Synapse Creature in charge of command.
How were they able to pinpoint the target so accurately in this thick fog? Because the thing was constantly emitting a blue psychic light, like a hundred-watt blue lightbulb. If not for the spore-mist obscuring it, it would have been visible for several kilometers in every direction.
It was a grotesque amalgamation of brain and sinew. Its huge head accounted for nearly four-fifths of its body, the brain tissue practically exposed, with complex gyri pulsing along with the ominous blue psychic glow.
Invisible psychic commands radiated from it like ripples, precisely coordinating the firing timing of every Bio-Artillery piece.
This... was also quite normal. After all, to coordinate hundreds of Hormagaunts and Termagants to act in unison, executing complex tactical flanking maneuvers and artillery synchronisation, the Synapse Creature's brain tissue must be highly developed and its psychic field must be tremendously potent. Anything less would be impossible.
The enemy was revealed. So, what was the next move? The Astartes unanimously turned their gaze to the Ultramarines Sergeant leading the squad.
The Sergeant, for once, was slightly stumped. If the target were merely muscular and well-armed, they could simply charge en masse and fight to the death; the outcome would be uncertain, but the path clear.
But the Synapse Creature before them was clearly a hyper-psychic type. As a seasoned veteran, he instantly analyzed several potential assault plans, but the success rate of each was pitifully low.
He could sense the intensity of the psychic power—a pure, overwhelming force of will.
If they charged rashly and the creature reacted, it wouldn't need to do anything else but psychically hold the dozen of them in place for a few seconds.
If the nearby Bio-Artillery pieces, serving as guards, turned and unleashed a salvo, would the dozen Astartes have a chance of survival?
Space Marines were the Spear of the Emperor, not mindless berserkers. The life of every Battle-Brother was extremely precious and could not be wasted on a reckless charge.
At this moment, the Sergeant found himself almost missing the Helldivers' Ogryns. If that group of giants were here, there would be nothing to deliberate; they'd simply charge forward with battle cries, and all thought would be unnecessary.
Therefore, after a brief period of consideration, the Sergeant made the most secure decision.
"Maintain silence. Do not make a sound," he ordered all the Battle-Brothers via the comms. "I am contacting the rear for artillery and Thunderhawk Gunship support."