Originally Posted by
plawolf
Not exactly. He lead a small detachment of Fists in a suicidal boarding operation to slow down a massive chaos fleet. When the rest of the fists showed up, all they found was his severed hand when they boarded a battleship.
It was never said that he was killed, just that the Fisits assumed he was.
The timing of the incident was also worth mentioning, as at that time, iirc, Dorn was the last Primarch still alive and active, and sections of the Imperium were starting to deify him, much to his ire.
Personally, I find it unlikely for the Primarch to be taken out during a boarding action, since the design of a ship would force attackers into bottlenecks so they would be able to fully capitalise on any numerical advantage.
My personal view is that if Vulcan can survive being blasted by vehicle mounted heavy weapons or artillery when faced against traitor legions and Primarches in open ground, Dorn should be able to take care of himself against 'mere' traitor marines in a maze of corridors on a starship. The fact that he was operating amounts a fleet of enemy ships at anchor would also give him the opportunity and means to 'disappear' if he wished by taking over one of the smaller ships and then jumping out to wherever he wanted to go.