Quote Originally Posted by hamishspence View Post
Where's it stated that Dorn was still "in charge" when Guilliman introduced the Codex Astartes proposals?
Dorn was Warmaster when Horus turned. That puts him in charge. Just as Horus was before him.

If anything, Guilliman, as "Lord Commander of the Imperium"
Source? Nevermind. In looking for other things I found it. After the Heresy, Dorn left on a Crusade (for his failure that is the Emperor getting stabbed), which basically left Guilliman in charge. When he got back, Guilliman was basically in charge of everything and said "Codex, now."

"Dorn called Guilliman a coward for not fighting at Terra, while Guilliman called Dorn a rebel"
Guilliman can say whatever he wants. Dorn could've been a 'rebel' for whatever reason Guilliman could make up. The Codex is designed to reduce political power by reducing military might. If everyone else does it and you don't, that makes you a rebel.

And Deathwatch: First Founding suggests that Vulkan may have lead his legion for 3000 years:
So did most of the Primarchs.
Anyway, I did some research on the Timeline of the Primarchs quite some time back but I can't find the post. My Search-Fu is pretty bad. Usually other forumites have done it for me.

When Vulkan left, the remaining Primarchs were Dorn and Corax.
Dorn was sad when Corax left.

Dorn was last.