The war to eat and be eaten began without announcement.
In low orbit above Gryphonne IV, the Adeptus Mechanicus fleet and its ring of orbital defense platforms formed the first line of resistance. Laser arrays and lance batteries opened up against the incoming hive fleet in sustained bombardment, the energy output sufficient to visibly scar the void between them and the target. Torpedoes followed in mass salvos, their drives burning bright against the dark as they curved toward the Tyranid ships.
The hive ships absorbed it.
Chitin biological armor hundreds of meters thick at the hull took the impacts and distributed the force through layers of dense organic material that had evolved specifically to survive this. Bio-ships that were mortally struck fell out of formation and drifted. The formation itself continued forward. From the cavernous biological launch bays that ran along each hive ship's flanks, void organisms poured outward: fighter bio-constructs moving in swarms beneath the cover of the larger Kraken-class escort creatures, driving hard toward the Mechanicus fleet.
The Mechanicus defense turrets cycled at maximum rate, building overlapping fire corridors that would have destroyed most conventional attackers. The Tyranids were not conventional attackers. After enough boarding organisms had cratered themselves into the void shields of individual ships, embedding their biological hulls into the armor beneath, hundreds of Genestealers poured from each impact site into the interior passages, and the turrets defending the exterior could do nothing about what was already inside.
The Skitarii Vanguard aboard the affected vessels moved to meet them in assault groups, closing from multiple directions through the ships' internal corridors. The Vanguard were radiation sources in humanoid form. Against flesh-and-blood organisms, their proximity was lethal in ways that armor could not address. They were the most effective counter the Mechanicus had for what was now moving through its ships.
They were not enough to stop the tide.
More hive ships came through the orbital engagement than the defense could prevent. Each one that broke through took further fire from surrounding vessels in passing and did not stop. As they reached the upper atmosphere, they released their first drop payloads: millions of spore units, tumbling and wriggling against the sky, catching what light filtered through the void above.
Soldiers in the trenches could see them with the naked eye.
"All Hydra platforms, open fire immediately."
Nolan did not raise his voice. He was watching the battlefield projections, green light tracking across his face as the contact density built.
Across Gryphonne IV's surface, the quadruple autocannon mounts of the Hydra flak tanks came alive simultaneously. Skyfire missiles followed in rapid sequence from the launcher batteries. The sky above the industrial hives became a continuous field of detonations, fire and thick smoke obliterating visibility from ground level upward. For a stretch of minutes the bombardment was almost total.
Many spores still reached the ground.
Those that came down in the open ground beyond the fortified perimeters were hunted by rapid-response units before they fully opened. Many were eliminated. Not all. By the time the first biological casings had cracked and their occupants had assembled, the screens in front of Nolan were showing organized contact clusters moving toward the outer defensive lines.
"Ground forces, commence hellstrike and cyclone missile fire to clear the advance. Begin attrition against the forward mass now. Order all logistics manufactoria in the hive cities to begin full production of ammunition and vehicle components immediately."
Hellstrike missiles arced from firing positions inside the foundry complexes in overlapping waves. Cyclone launcher batteries added their own contributions. Where the salvos hit the forward Tyranid elements, the detonations rolled into each other, fire building on fire, the shockwaves compounding until the ground itself appeared to move. Entire advance formations were consumed in the first minutes. More followed behind them.
The forge world's advantage was exactly what Nolan had calculated: as long as the hive cities held, the industrial capacity to produce ammunition and replacement vehicles operated continuously. The Tyranids could absorb losses at a rate that would destroy any other defender. Gryphonne IV could absorb the ammunition expenditure.
For the moment, the equation held.
In orbit, it did not.
The Mechanicus fleet lost ships in numbers that the defense platforms could not compensate for. The orbital stations took sustained biological bombardment that their armor ratings had not been designed to withstand indefinitely. One by one, the platforms went dark. When the last of them ceased transmitting, the void above Gryphonne IV belonged entirely to the hive fleet.
The second drop followed immediately.
Spore pods fell in numbers that dwarfed the first wave. Where the first wave had been a test of the surface defenses' coverage, this was a saturation strike. The sky filled with descending biological material from horizon to horizon, and the Hydra batteries could not intercept all of it.
From within those pods, as they cracked open across the surface, the larger organisms emerged.
Twenty-three of them, over the span of a dozen hours. Tyranid bio-titans, organisms built to a scale that matched the Imperium's own war engines: Hierophant class, most of them, moving with the ground-shaking stride of creatures forty meters tall and grown specifically to destroy armored fortifications. Below them, the smaller organisms flowed in a purple-tinged tide that seemed to have no edge and no end.
Nolan stood up.
He looked at the shapes visible even at this distance against the smoke-hazed horizon and took one breath.
"Gryphonne Titan Legion. Engage at your discretion. Your only priority is the bio-titans. Nothing else. Eliminate them before they reach the industrial hive walls."
The Titan Legion moved.
They spread outward from their staging positions with the grinding deliberateness of walking fortresses, each step carrying enough weight to crack ferrocrete, the god-machines of the Mechanicus deploying into battle formation with the unhurried confidence of weapons that had no equal on a conventional battlefield. Their void shields flickered as targeting systems locked and weapons charged.
An Imperator-class Titan turned its Volcano Cannon across the field of engagement.
The beam that followed crossed the full width of the engagement zone in an instant, the most powerful directed-energy weapon ever mounted on a ground vehicle, and struck a Hierophant bio-titan mid-stride. The creature's forward momentum carried it three more steps before its biological systems registered the catastrophic damage to its midsection and it collapsed, thrashing, into the earth.
Around the advancing Titans, the Knight suits of House Winter and House Cadmus moved in escort formation, faster than the god-machines and more maneuverable, their lances and heavy stubbers keeping the smaller Tyranid swarms from closing with the Titan legs. A Knight had no answer for a Hierophant. Against Hormagaunts and Warriors trying to bring down a Titan from close range, a Knight was exactly what was needed.
The assault formation engaged: ten Warhound-class and twenty Reaver-class Titans pressing forward to hunt the bio-titans directly, using their speed advantage to dictate engagement range. Behind them, the Warlord-class and the two Imperators held the firing line, their heavier weapons reaching over the assault formation and into the Tyranid mass beyond, disrupting any biological unit attempting to mass for a charge against the advancing engines.
For a time, the battlefield tilted.
Then the light above began to change.
The hive ships that held orbit above Gryphonne IV opened their bays again, and the spore pods fell in a continuous downpour that was no longer a wave but a condition of the sky itself, an unbroken density of descending biological material that the anti-air batteries could reduce but not prevent.
The attrition equation had revealed itself in full.
The hive fleet would keep producing. Gryphonne IV would keep producing. The question was which side ran out first, and it was a question with no fast answer.
The tug of war had begun.