Board Thread:Warhammer 40k General Discussion/@comment-14745711-20140928092626/@comment-25482306-20140930095115

There's an assumption here that all the chapters would flock to the returned Primarchs. Only those with shared gene seed are definitely going to do so, others... not so much. Especially those of the later founding's who do not always know which of the original 18 Legions they take their heritage from in the first place.

One other thing is that Gullimans first move could well be to secede Ultramar from the Imperium, he already considered it once during the Heresy. Basically creating a whole new Empire with a strong possibility of all Ultramarine successor chapters being re-called and reporting to one commander. That's going to be popular back on Terra.

However, whilst you might not see civil war right off the bat, as these things take time to deal with in a galactic Empire, you would end up with a much more fragmented and paranoid political situation, it would be chaos with no one knowing what's going on or who to believe.