Octarius War
The Octarius war is the most hilarious and fail venture the Imperium has ever made.
The Imperial Guard were having their asses handed to them by the Orks on the planet Ghorala in the Octarius system. Inquisitor Kryptmann leading expert on the Tyranids decided that the best solution would be to sic a recently captured swarm of Tyranids on the Orks and letting the two fight it out, the IG would then mop up the remaining survivors. The obvious flaw in his plan of course is that both Nids and Orks thrive on war, meaning the survivor will emerge much stronger than ever before. The conflict has currently devolved into a massive meat grinder and the Orks are fucking loving it.
After the enactment of this plan Kryptmann was fired from the Inquisition for being a fucktard.
This tale is notable for being one of the few bits of fluff in the Nid 'dex where they don't get their arses handed to them by space communists, poncey faggots or fucking smurfs