Note: I own neither Strike Witches nor Warhammer 40,000.

The 41st millennium. It is an era of unprecedented strife and bloodshed that threatens to engulf what has left of the Imperium of Man.

Thousands of years ago, the Imperium was at its apex, roaring through the galaxy in its quest to unite every stranded human world and remold the stars in humanity's own image. The spearhead of the Great Crusade was none other than the God-Empress of Mankind, a divine figure perfect in every way, be it mind, body, and heart. It was her godlike mastery of psychic energy that has linked every corner of her realm, and it was her insurmountable vision and tenacity in battle that led the Imperial forces to countless victories against the wretched aliens that stray into the path of humanity's conquests. Outside the battlefield, however, the Empress was a benevolent, charismatic figure, who ushered a golden age of human settlement, technology, and culture. Such was the bliss while the Empress walked amongst mortals.

Now, the once-beautiful, omnipotent God-Empress now lies dormant, mortally wounded by the most hideous treachery inflicted upon her at the peak of her power. Upon her Golden Throne, her warm, bleeding body has been powering the Astronomican for millennia, ensuring that her dream of a unified human empire is sustained as long as possible. Xenos, who once trembled before the awesome might of the Imperium, now gnaw upon its edges in a furious orgy of bloodbath and destruction. Worse still, the Forces of Chaos, the same powers that nearly slew the fair Empress long ago, are now drilling its corrupting tendrils deep within human civilizations, eager to convert any vulnerable individual to their twisted, maniacal ends. Humanity, just as it has been throughout its harrowing existence, is once again under siege.

But the God-Empress has one last trick up her sleeve. Of all the psychoactive species throughout the galaxy, humans are unique in harboring psychic potential in a minute fraction entirely within the female gender; That is, only the females of the race can ever hope of being born as psykers, or "Witches". Since the dawn of human civilization, these Witches were called to serve the human race, ranging from making mundane existence convenient to taking up arms and risk their lives for the survival of the entire species. Legend even has it that the God-Empress herself embodies the thousands of spirits of Witches who have lost their lives for humanity.

At the beginning in the Great Crusade, the Empress endowed the greatest Witches among humankind with portions of her genetic material, creating an elite organization of immortal, semidivine warriors who devote themselves to purging the galaxy of all those who oppose the glorious dream of their leader. Together, they struggled and triumphed against all odds in the greatest of battles, and they even stood together on the eve of the Empress's own tragic fall. The boundless piety to their spiritual mother still goes strong thousands of years after her "death", and these Angels of Death shall never cease to roam amongst the stars until every xeno, demon, and heretic draw their last foul breaths.

The Great Crusade of the God-Empress shall continue, for they are the Adepta Astartas, the Space Witches.