Board Thread:Warhammer 40k General Discussion/@comment-3416287-20131218143514/@comment-96.237.238.119-20131218191511

The Imperium has definetly used asteroids as weapons on at least one occassion during the Macharian Crusade. Macharius (Lord Commander of the Crusade) came across an independent planet who's technological feats even surpassed The Imperium. After all attempts to conquer the planet had failed, Macharius ordered a nearby passing comet to be redirected by his fleet and sent crashing into the planet. Depending on your sources, this act either forced the planets remaining population to surrender, or destroyed the entire world.

As to the second part of your question, I'm fairly certain the Imperium does indeed use various WMD's on it's enemies, but ONLY does so as the ultimate last result. This is because there are not enough worlds in the Imperium to allow for a widepread use of Virus Bombs/Cyclonic Torpedoes/Orbital Bombardment, and so they are only used in the ultimate worst case scenario. Even worse is the fact that in the most recent 1000 years the Imperium's forces have been growingly strained because of events like the 13th Black Crusade, the Wars for Armageddon, Tyranic Wars and others. Which means that the Imperium lacks the manpower and firepower to take on Orks/Necrons/Tyranids full on.