The Dark Angels fleet made the jump. They did not notice that, in the shadow of a planet several light-years behind them, a small warship belonging to the Ordo Hereticus, covered in sacred "I" symbols, had quietly followed them.
At the same time, because the Dark Angels did not want anyone within the Empire to know where they were going, they did not formally respond to or file the emergency transmission. After all, once they had retaken and purified the planet and completed their secret mission, they could simply submit the report afterward.
Normally, that would have been fine. Even if other Chapters received the message and came to assist, the Dark Angels would have finished everything by then.
But sometimes, it was the unexpected that caused trouble.
Another Chapter happened to be passing through a nearby sector. Their distance from the Gladius System was almost the same as that of the Dark Angels, and they received the distress signal at roughly the same time.
After formally answering the call to battle, the fleet belonging to the battleship Pride of Russ likewise jumped toward Gladius.
This was not supposed to happen. In an ordinary crisis, only one Chapter would answer.
There were not many cases of Space Marine Chapters working together, either. The universe was just too damn big. Unless they were successor Chapters that had always been close, they were unlikely to act together.
For example, during the Second Founding, the Dark Angels had split off successor Chapters such as the Angels of Redemption, Angels of Absolution, Avenging Angel, Angels of Vigilance, Guardians of the Covenant, Disciples of Caliban, and more. Those Chapters now bore the responsibilities of Space Marine Chapters independently, but because of their close blood ties, they got along well with one another.
And where there