The Imperium's reinforcements were deployed to Armageddon, bringing welcome and immense changes to the overall war.
The massive expeditionary force, composed of dozens of Astra Militarum regiments from different worlds and star systems, filled the gaps along the front. These well-trained, well-equipped Astra Militarum soldiers were far beyond comparison with Armageddon's hastily conscripted militia and its original Planetary Defense Force.
The once-precarious Styx Line had successfully held with the aid of the Space Wolves Chapter and other Astra Militarum regiments, and had become even more solid than before.
Now, they could finally catch their breath amid the Orks' ceaseless assaults. The soldiers who had fought to the death in their positions were given the precious chance to rotate out.
Those armored vehicles, long neglected and covered in hastily welded plates and bullet-pocked dents, could also be withdrawn to the rear for more thorough and complete repairs.
Large numbers of local soldiers worked alongside Astra Militarum regiments. Since the Horus Heresy, just as the Astartes Legions had been broken apart, most Astra Militarum regiments had likewise been divided up and assigned separate roles.
To prevent another rebellion from producing rebel forces of significant scale, nearly all Astra Militarum regiments in the Imperium were single-arms formations built around a particular style of warfare.
This left the Imperium's armies poorly accustomed to tactics such as infantry-armor coordination and advancing under creeping barrages. The Imperium's military was like a 200-supply force in StarCraft made up of only one unit type.
When you had a thousand-supply worth of good brothers, you would not waste too much effort micromanaging your soldiers' movements. F2A, all forces charge—that was the norm in Imperial warfare.
Wars they had failed to win could almost always be summed up in one sentence: there was too little time and too few soldiers.