Siege of Andrene

The Siege of Andrene was one of the most lamentable events in the history of the Incursors Space Marine Chapter, when their homeworld of Andrene was attacked and eventually overrun by the greenskin tide of WAAAGH! 'Da Green Herald'. In the end, the planet was overrun and had to be subjected to Exterminatus to ensure the destruction of the vile Orks.

History
The world of Andrene was always known the plague that were the Greenskins, and for a time, the local Astra Militarum regiments and Andrene Shield Guard had always managed to keep the local ork population down, to ensure the Orks could never become a threat. That all changed when an Ork calling himself 'Da Green Herald', rallied Ork populations across the sector. When warboss arrived into the Andrene System many Astra Militarum ships were taken by surprise and barely managed to put up a modicum of resistance. The Incursors Chapter's 9th and 10th companies, which had already been sent to intercede on behalf of the besieged system, then called for the entire Chapter for help. When the Orks invaded the capital world of Andrene they set upon the capital city of Thu'ak with an almost literal green tide, attacking the city and its inhabitants.

When the rest of the chapter arrived, the void warfare was so damaging that the 7th Company's flagship, The Anshanti, caused its warp engines to go critical and explode spectacularly, taking half of the doomed company with it. When the surviving companies made planetfall, the Incursors immediately set up defences in the cities around their fortress-monastery. With the chapter trying to signal for more reinforcements, there was no help to be had as all the nearby systems were also being assaulted by the Green Herald's forces. Any potential reinforcements were dealing with other threats or attacking the Green Herald's forces, and none could reach Andrene in time.

As the green tide made it to the outskirts of the city being defended by the Incursors, at first the Orks couldn't breach the city's walls, as the walls were heavily defended by Planetary Defence Forces and Incursors Astartes. It wasn't until the greenskins brought forth hordes of Ork Gargants, that they were finally able to break through the walls. Imperial Warhound-class Titans and Freeblade Knights did their best to repel the green tide but the Warhounds and Freeblades were severely outnumbered, and many of the initial defenders on the wall were killed. As the months progressed, more and more of the city was being held and taken by Imperial forces with the greenskins incurring heavy losses. It wasn't until the Orks destroyed Andrene's moon, Caden, by unknown means and used its fragments as missiles launched towards the cities, that caused massive devastation to both the Orks and Imperial alike. It was revealed soon after, that some of these larger asteroid fragments contained Orks inside them, as both a devastating weapon and troop transport.

The Incursors did as much as they could to hold the Greenskin tide back, even setting off nucleonic bombs along strategic points. The Chapter was forced to retreat back to their fortress-monastery with those refugees that were fast enough or lived near the Astartes' citadel, and those that didn't make it to the fortress-monastery in time, were left to the devices of the Orks. After about three and a half years of warfare, most of the planet was lost to the Orks. The outside of the fortress-monastery had become a pock-marked shelled-zoned of massive craters made by the fortress's guns or by orbital attacks. In fact, many Chapter Scouts managed to sow havoc amongst the Greenskin forces, causing groups of Orks to attack one another or damage their vehicles - anything to halt the advance of the oncoming 'green storm'. As night began to sweep across the planet, many scouts were confirming the deaths of The Green Herald. This confused many, and only when it was too late, did the Chapter find out that the real Herald was behind the WAAAGH! and using doubles to trick the Space Marines. With orders from the Chapter Master, the escort vessel known as the Tairven, plummeted from orbit onto a large grouping of Orks, taking a few prized Ork Gargants in the process.

While the Orks had trouble breaking throughout the fortress's void shields, the Incursors began their preparations to evacuate the planet, taking many of their relics, banners and emptying their Librarius and placed these precious items in transports, awaiting for their final orders. While many of the transports were in the middle of storing the Chapter's identity, the Orks finally broke through the shields. The remaining Astartes desperately tried to put up a defence against the unstoppable, frenzied Ork tide. Most of the chapter had begun running low on ammunition and their blades began to dull from overuse. After days of fighting, the Chapter's fortress-monastery was left burning. Some parts of the Librarius couldn't be saved, and soon, these fires were used by the Orks to huddle around, while several captured Chapter relics that fell into the clutches of Orks became trophies.

Many battle-brothers refused to retreat and wanted to fight to the last in the name of all their brothers that had been slain and couldn't be recovered. It was only after a great speech from the Chapter Master Nomeras Carva, that made several warriors weep and uplifted the spirits of all those that heard his words, giving them renewed purpose. This speech made the battle-brothers get out of their single-minded rage and allowed them to follow their orders to evacuate to the ships in orbit. Most of the 1st Company stayed behind, along with the few surviving Knight Freeblades to try and hold the Green Tide back as long as they could, to allow the ships to leave. When the ships began evacuating, the anti-aircraft cannons started to tear apart several of the smaller transports. When the rest of the surviving transports made it aboard the carrier vessels, the Chapter Master gave the order to enact Exterminatus upon Andrene, before an audible scream was heard. Following the order the Chapter subjected their homeworld to Exterminatus and immediately left their home system. Forever after, they would become a fleet-based Chapter.