With the expansion of the Stygian empire halted temporarily, the Imperium began planning and mustering forces for a counteroffensive. Some in the Ecclesiarchy wanted a war of faith declared, while others sought crusade to end the threat of chaos posed by the Stygian Empire. Whatever the official declaration the ponderous might of the Imperium was about to be brought down upon the Stygian empire. Unfortunately for the Imperium the spies and agents of the Alpha Legion had taken notice and Lord Magwar had a plan in place to deal with the coming storm.
The Flashfire campaigns
The first flashfire campaign began on the Imperial world of Laotia II. A small flotilla of two transport vessels and three infidel class raiders slipped the Imperial cordon and made it's way to the planet. The raiders fired up the planet indiscriminately as thousands of lighters, savior escape pods, and other drop ships unleashed a horde of cultists across the planet.
The hordes of mutants, cultists, psychers, and bio mechanical constructs cut a swathe of destruction across the planet. the attacks were however random though widespread. The flotilla departed however within hours of it's arrival leaving the horde behind to rampage. Imperial reinforcement were detached from the coming counteroffensive to put down the attacks and restore order. within weeks of their arrival the suicidal horde ha lost over 60 percent of it's strength to clashes with Imperial reinforcements.
The remainder of the force however went to ground and began a planet wide insurgency campaign so effective Imperial reinforcements were needed to maintain order and were unable to depart for a new offensive against the Stygian empire. Imperial tacticians calculated that 5% of the forces dropped on Laotia II were in fact trained heavily in insurgency.
And so in the coming months more flotillas slipped through the lines to drop expendable cannon fodder along with trained insurgency experts onto no fewer than 17 imperial worlds. Most of the incoming imperial reinforcements were now being sent to stomp out the fires of these new attacks, including the forces previously dedicated to launching a counteroffensive. These attacks began to be known as flashfire attacks as they happened suddenly, threatening to blaze out of control and topple the planet, and had to have a large imperial garrison left after the initial battles to keep the fire from reigniting.
The Shadow War
Even as the flashfire campaigns were being initiated the shadow war increased in tempo. Chaos assassins and sleeper cells would strike behind imperial lines only to disappear again. Imperial forces secretly worked to stop these attacks as well as inserting agents to spy and sabotage the Stygian empire. The shadow war raged for intelligence, and secret control of the sector. It went generally unnoticed amidst the sector spanning war. After all with tens of thousands of people dying every day in the war what did the loss of one or two individuals a day matter.
The Wars Grind On.
And so the Stygian wars raged for the next two years in bitter stalemate. The shadow war had revealed to the Imperium some of Lord magwar's plan, along with other useful information. One such tid bit was the Alpha Legion turning use of p.o.w.'s into spawn, battle servitors, or sacrificial offers to summon daemonic aid.
The Adeptus Astartes forces began to raid the Stygian Empire worlds in response to flashfire attacks. These met with mixed results though the Apocalypse Angels chapter had a high success rate along with elements of the Raven Guard that had come to aid the Imperial cause.
And so the Stygian Wars rage to this day across over two dozen worlds, hundreds of orbitals and remote outposts, in the depths of space between worlds, and hidden in the cities across both empires. it sees both sides raiding the other while gathering strength to launch major offensives. It sees small detachments joining both sides daily in an effort to tip the scales, while mad genius's on both sides develop new weapons with which to win a series of wars that has already seen chemical and even atomic weaponry used. In this dark millennium with a conflict this large there can be no pity, no peace, only war.