Extract from 'Our Darkest Hour: The Ork Invasion of Kallax', by sub-Commandar Reynor Armsworth, Kallax III PDF.
"While it was inevitable that the massive Ork horde would eventually reach the walls of Mercatura Hive, it was far from certain how quickly they would reach it and how much of their formidable forces would be intact when they got there. At this point it was the job of the Imperial Commanders to harry the Ork forces as much as possible with their most mobile divisions in order to distract, slow and disrupt whatever passes for order in an Ork Waaagh!
During this period I had the honour of being one of the many communications officers for Tactical Command based in the Trade Precinct of Mercatura Hive. I witnessed many extraordinary engagements during this part of my career, some roaring successes, others dismal failures.
As with most wars, the eventual outcome pivoted on just a few key engagements. For a time I was posted as a communications liaison officer for the Praetorian IV Mechanised Infantry who fought in one of these most important of battles. Their Commander at the time, Colonel Animus Winterborne, had already made himself famous from his daring (and perhaps foolhardy) activities in the Timus Mountains at the start of the campaign, and now was to take part in an even more important event.
Research Station Epzoid Kappa was a rare joint venture between Imperial and Mechanicum personnel. While the story of how such an unusual working arrangement came about is an interesting tale in itself, it is of little relevance to the battle that put a final end to its use.
The research station became of tactical importance primarily due to its incredible high strength aerial scanning array. While its intended use was to study the extraordinary electrical storms and meteorological affects that developed across the plains in the summer months, it had soon been discovered by the Imperial Commanders that it could be used as a radar system with unparallelled accuracy. Its intricate and revolutionary design meant it could pinpoint aircraft within a couple of meters, in real time, through any clouds or weather effects and with enough information on their direction, size and exhaust wake to work out exactly what was in the air and when.
For a few days this gave the Imperial forces such a tactical advantage that they were able to completely dominate the air space above the plains even though their aircraft were outnumbered more than fifty to one. In this brief period countless airstrikes were unleashed on poorly defended Ork ground forces, slowing them down and buying precious time for the defenders of Mercutura Hive.
Dumb as a single Ork appears to be, it seems certain that one of them figured out where this technical marvel was located and planned a counter move. A massive Ork aerial force descended upon the facility, large and fast enough that no matter what information was gathered on it, it could barely be slowed before it had carpet bombed the entire facility.
The Orks were not wasteful in their destruction however, as they used almost exclusively incendiary ammunitions to wipe out any resistance offered. While this preserved the precious equipment that the Orks no doubt planned to utilise for themselves, it also saved the lives of some of the facility's inhabitants who were lucky enough to be in more secure bunkers. These few survivors were able to report back to Tactical Command and give just enough warning so that Colonel Winterborne's mechanised infantry could arrive in time to meet the Orks on an even footing."