Robickai ran like... well, like there was a xenos horde hot on his heels. As he passed several of his platoon mates he sent a quick prayer of thanks to the Emperor for the willpower that had seen him keep up his cardio training. As the compound gates emerged through the smoke, Robickai saw that they were closing fast, with many of the platoon still on the wrong side of the gates when they closed all the way. He put on a final burst of speed, and shot through the gap just as the gates boomed closed.
He skidded to a stop, and paused for a moment to catch his breathe and look around. That snot-nosed LaVeer kid was leaning with his back to the gate, his chest heaving and his eyes large with fear. Where's all his parade ground cockiness now, wondered Robickai. He heard a barely coherent shout, something to do with the buildings, and turned to see the Caul kid charging off towards the command buildings, a few others trailing in his wake. It made sense to clear the buildings, but the priority should have been securing the walls and gates. Having got his breath back he turned back to the gates, intending to see if they could get any of their stranded comrades in through them before the Orks hit it. If LaVeer tried to stop him, well, too bad for him.
He only got two steps when a burning flyer came screaming out of the sky and impacted not far from the gates. The impact knocked most of the men off their feet. Robickai struggled back to his feet, the dull throbbing that had been present since the truck crash now a head-splitting blaze of pain. He raised a hand to his ear, and was not surprised to see it come away bloody. He shook his head, trying to shake away the pain, and returned his attention to the gates. Just as he reached them a human voice boomed out beyond the gates, augmented with some sort of speaker system.
Robickai ran for the stairs beside the gatehouse, making the rampart just as the voice boomed again.
"Run! Run you Coward. I expect a weakling like you would chase such puny trophies!"
Robickai saw the small horde of greenskins, backlit by the burning wreckage of the flyer, turn at the roar, and something large flew out of the smoke and flames, striking one of them between the shoulders, knocking him to the ground. Robickai recognised what it for what it was, and ducked behind the rampart, shouting "Bomb!" to those that had come up behind him. When there was no immediate detonation, he raised his head to view the scene again, just as the flyer wreckage detonated. In the flash of the explosion, another horror emerged from the smoke, silhouetted against the flaming wreck. Humanoid in shape, of proportions distinctly unnatural and unsettling to the human eye, but moving with a speed and grace that something that bulky had no right to, it hit the confused orks with an audible crash, and the butchery that ensued was truly astounding.
As this was happening, it finally sunk into Robickai's brain why this new monster was so familiar to him. It was of a shape that every Imperial citizen instinctively recognised, as statues of creatures just like this one looked down on them from temples and civil buildings all across the planet. Robickai had always thought that the statues were exaggerations of the real thing, as all depictions of Imperial saints and heroes tended to be. But no, the evidence was only yards from him, killing with a ferocity and brutality up until now he would have found unimaginable. "Astartes," he mumbled to himself. "Dorn's balls, that thing is on our side?"
The shouting from the men around him, who only took a second more than him to realise what they were seeing, became a din. "Space Marines! We're safe, the Space Marines are here!"
Robickai looked at the battle again, still mesmerised by the methodical butchery, but he noticed that no other Astartes emerged from the smoke in support of their brother, and despite his speed and skill, this lone warrior could very well be swamped by sheer weight of numbers. "Help him!", he roared over the din of battle as he raised his rifle and started firing into the green rabble, fairly sure the Astartes battle plate would prove effective against any stray shots he took. The men around him followed his lead, and volleys of las fire started having an effect on the greenskins, if only by splitting their attention between the compound and the lone Astartes.