Yes, I know given the period that this story is in the Angels would not know the names of the Tyranids, but I did that just to make it easier for the readers to know what I was talking about.

Angels of the Aquila
Purging of the Behemoth

A Second Founding Chapter of the Ultramarines, the Angels of the Aquila were sent on the world of Abiram on the Eastern Fringe, where they were trapped in a vicious warp storm. They were effectively trapped until it dissipated in M41. This was not good news though, as Hive Fleet Behemoth, which sent a fleet down to attack the Angels, detected them. Now the space marines fight for their lives against the vile tyranids...

The ten members of the scout squad advanced through the city, bolters sweeping the surrounding the area or their patrol, watching out for any tyranid monstrosities. Sergeant Cyprian's Auspex suddenly flashed, but before anyone could react, five Genestealers leaped from an alley and ripped through two of the scouts, their claws easily tearing through their armor. Bolter fire ripped through three of the creatures, before combat knives could be drawn. Another scout was down before Sergeant Cyprian screamed over the sound of the fight into his vox.

+"Multiple contacts in Sector 27-B. Genestealers, possibly more. Requesting Reinforcements."+

Having hearing this, Commander Macarius instantly sends Squad Fabian and Assault Squad Wyatt to help the endangered scouts. The tracks of Fabian's Razorback thundered against the pavement as the assault marines took flight, hoping to reach their battle-brothers in time. Fabian urged the drivers to drive faster as the Razorback was pushed to the limits, knowing there was no time to waste.

As soon as the initial Genestealers had been killed, Cyprian urged his remaining scouts into a manufactorium behind them. They had set up on the second floor, as the members with sniper rifles un-slung them and peered out into the city. It was not long until more tyranids arrived, this time with scores of gaunts led by a brood of warriors.

"Snipers!" Cyprian yelled. "Aim for the larger beasts!"

Bolter fire raked through the lesser gaunts as one of the snipers shot at one of the Warriors. His shot bounced off its head crest as it shot back. The scout fell back as the corrosive acid dissolved through his skin. The sergeant ran over, picking up the sniper rifle that was dropped. Luckily, it was not damaged, so he aimed and shot the same tyranid, this time slamming it in the eye. The combined shot of the second sniper ended the beast, but it was still not enough. Another of the 10th Company had fallen, and the beasts were starting to claw their way into the manufactorium.

Luckily, there was a clear view to the ground floor, a prime spot for tossing grenades. Their bolters were still scything through the gaunts, but there was too many as the scythe-armed ones finally broke through.

"Tenth Company! Grenades!" commanded the sergeant as multiple frag grenades fell onto the first floor. Multiple explosions followed, but the tyranids still swarmed in. Their ammunition almost spent, Cyprian knew they could not survive as he heard bolter fire from outside. As he looked out, Assault squad Wyatt drop from the sky, engaging the smaller beasts that were outside. He could see Wyatt's power axe hack into carapace left and right, as easy as going through paper. Soon after, a Lascannon bolt slammed into the side of one of the two remaining Warriors, punching a gaping hole in its side. Squad Fabian disembarked from the Razorback and assisted the assault squad in eradicating the gaunts, while the Razorback continued to shoot at the Warriors.

This gave the Scout squad new hope, as Cyprian urged his troops into battle. Hormagaunts were already jumping up to meet the scout squad, but they were ready as bolter fire raked through the first wave, tearing through their carapace and into their organs. After emptying his last clip, Cyprian drew his combat knife again and charged headlong into the have of beasts, his battle-brothers following. Within a few minutes, it was over. Cyprian's squad had lost another two soldiers, with Fabian's squad losing one, and Wyatt's assault squad had one that was unable to fight for the moment, but would recover.

Sensing that more would come, the three Space Marine squads re-loaded their weapons and set off again. Before long, the remaining four scouts had spotted them, this time with even greater numbers, with a broodlord leading them.

+"Targets located. Multiple genestealers accompanied by broodlord, extra support requested."+

The wind was heading the opposite direction from where they were looking, so the tyranids did not know where they were. The sound of an incoming Rhino combined with the whine of the Assault Marine's jump packs alerted the Broodlord and his genestealers to their presence. As soon as it did, the scouts opened fire, immediately shredding three of the genestealers. Squad Fabian emerged from their transport and started firing upon the monstrosities. Knowing not to get into combat until needed, the assault squad fired their bolt pistols and burned them with their flamers. Eventually, close combat was the only option as the Genestealers got too close for comfort.

Additionally, Commander Macarius decided to enter this fight personally, and set off with his command squad in one of their few Land Raider Crusaders into the depths of the city to root them out. His allies were not far off, and he knew this city like the back of his hand, allowing him to get there with top speed.

Sergeant Wyatt hacked at a hormagaunt with his power axe and blocked the slash of another with his storm shield, then tore through its midsection. One of his assault marines were already down, another wounded. He did not know how the other squads were faring, but it did not look hopeful with the amount of creatures left. The marine next to him had his arm tore off by a genestealer as Wyatt noticed the Broodlord. Standing at twice his height, it roared a challenge as it charged the sergeant. Wyatt stood defensively, prepared to take its charge, as the Broodlord was thrown aside by a pure-white ball of heat. Looking to his left, he saw the Land Raider Crusader, charge into the midst of the tyranids, Hurricane Bolters and Assault Cannon blazing, its front hatch dropped and Macarius and his loyal command squad jumped straight into combat, power weapons glowing brightly as they went through gaunt after gaunt.

After a few minutes of ferocious combat, the fighting was done, and the steaming remains of dozens of tyranids lay on the ground. As Commander Macarius went to embark in the Land Raider, he heard sounds of heavy fighting as his earpiece crackled to life.

+"Mass of Tyranids storming the Stronghold. Multiple Carnifexes and Hive Tyrants inbound, all units, report to the Stronghold"+