Unsure the battlefleet stationed above Macragge was enough to stop the Tyranid assault, a ground force was prepared just incase. But would this be enough?
Via Lexicanum
Hive Fleet Behemoth, since its appearance in the Galaxy, had been advancing with unprecedented speed through Imperial worlds. Marneus Calgar, Chapter Master of the Ultramarines, declared that the Hive Fleet would be halted at Macragge before it drove deeper into the heart of the Imperium or before it consumed more of Ultramar. It had to be stopped at Macragge or another chance to stand against it would not be possible for several hundred light years.
Forewarned of the impending Tyranid attack by Inquisitor Kryptman, the Ultramarines fortified their homeworld’s already formidable defences.
Above Macragge, the Ultramarines marshalled an enormous battlefleet, including Starnova-class orbital weapon stations, dozens of warships, the Ultramarines’ mighty Battle Barges, heavy cruisers of the Ultramar Defence Fleet, a ragtag collection of lightly-armed merchantmen and privateers, and the requisition of every single space-worthy vessel fit for combat. Meanwhile, a series of defenses were carefully constructed on the ground; if the Tyranids could not be stopped in orbit, Calgar’s plan was for the defenders to fall back to the planet’s polar fortresses and hold out until reinforcements arrived. When the Tyranids arrived, Macragge was ready for a fight.
The Tyranids, upon arriving in the system, were however not daunted in the least by the tremendous defences and without delay launched their assault. The defenders blew apart countless waves of Bio-vessels as they sped towards the planet, but with every wave more and more Mycetic Spores managed to break through to the planet’s surface.
As the Tyranid creatures made planetfall, the land battle began. Calgar divided his forces into three armies. The primary and secondary task forces, composed of most of the 1st Company and Ultramar Planetary Defence Forces, bolstered the polar fortresses on the north and south poles of the planet; whilst Calgar led the largest taskforce, composed of the entire 2nd Company plus elements of the 1st, 5th and 10th Companies , in a series of rearguard attacks to attempt to slow the Tyranid onslaught and buy time for the 1st Company to further fortify the polar fortresses.
At first the Ultramarines slowed the Tyranid advance for some time. But even under Calgar’s incredible leadership, the Imperial forces were only delaying the inevitable oncoming horde and eventually Calgar made the decision to withdraw his forces further north. At the same time, the Sirocco Starport was infiltrated by Genestealers, which destroyed much of Calgar’s shuttle fleet along with its pilots and Auxilia defenders. Having lost the bulk of his Auxilia forces but still needing to slow down the oncoming horde, Calgar set himself to making a stand at Cold Steel Ridge.
