Warsmith
Warsmith is a rank/title employed by the Iron Warriors. Given to the leaders of the legion's various Grand Companies. The Warsmiths each have a number of captains who in turn command a regular Company, placing the Warsmiths in positions akin to that of Chapter Masters. Warsmiths are highly skilled individuals: both in skill of arms and at siegecraft. They must also maintain a certain degree of savvyness amongst their equals and direct subordinates: if a Warsmith is killed the victor might absorb his opponent's Grand Company, and a good number Warsmiths have obtained their rank by killing its previous holder. One of the most famous Warsmiths is Honsou, who has a great record in getting shit done.
It is interesting to note that the position of Warsmith can be held even when its holder is interred into a Dreadnought, assuming they don't go insane (well, too insane by Chaos Space Marine standards). An example would be Berossus from Graham McNeill's Dead Sky, Black Sun.