Clearly, not very much. And why are you assuming that war is a foregone conclusion? The Emperor of Mankind enacted the Great Crusade to reclaim the lost human colonies and ensure the safety and peace of mankind. He doesn't seek war for the sake of war. I have no reason to believe that the Emperor, who has been shown to be a genius of immeasurable magnitude and an impossibly powerful Psyker, would declare war on new entities who aren't hostile or associated with the Chaos Gods. If we're talking post HH Imperium, then war is much more likely. [spoiler]Full disclosure, I know about as much of Dr Who as you know about Warhammer.[/spoiler]