Board Thread:Warhammer 40k General Discussion/@comment-25618639-20141119150740/@comment-6078851-20141205170458

i too shoulda been more clear: when i said the high lords are the biggest problem for returning primarchs i also meant the inquisition and the ecclesiarchy too as they all share the same goals and views - "we rule the imperium and such rule means that we are right. anyone who gainsay's us is heretical and a traitor to the imperium."

and when you consider that these three bodies control almost the entire imperium they have, by far, the numerical and strategic advantage in a civil war. they control the imperial guard, the imperial navy, adeptus sororitas, all propoganda. pretty much the only thing they don't control between them is the adeptus mechanicus and astartes.

while any primarch will instill almost immediate loyalty in anyone they meet, in a civil war they won't get that chance much: with the control of propoganda it would be very easy to convince the majority of the imperium that any appoaching astartes fleet is renegade and led by a traitor. this then leads to planets pre-emptively defending themselves, almost certainly on the orders of the inquisition, against the approach of a primarch. any inquisitor can infiltrate a planet and start spreading the idea that astartes have become corrupted.

there's roughly 1 million astartes and an astartes is considered to be equal to 10 or 100 men. so a straight up slugfest would require at least 10 million gaurdsmen and at most 100 million to take on a combined astartes fleet. the problem is that there's billions of guardsmen, occasionally billions on just a single planet, and that astartes are very widely spread, so such a civil war, even with primarchs, would be very difficult to win for the primarchs. such a civil war is always going to be heavily stacked against them.