The Duke (公 gōng) was a noble title ranking above marquis and below king. Enfeoffment as a duke often came with a large fief and special honours, and in the late Han and Three Kingdoms it was frequently a prelude to the title of king or to the founding of a new dynasty.
Role in the hierarchy
Dukes stood at the top of the noble hierarchy below the king. The emperor could grant them the nine bestowals (九錫)—ceremonial gifts and privileges that signalled exceptional favour and often foreshadowed a change of dynasty. Accepting the nine bestowals was a formal step toward declaring a new regime.
Cao Cao and the Sima
Cao Cao was enfeoffed as Duke of Wei (魏公) in 213 and later became King of Wei (魏王). The Sima family followed a similar path: Sima Zhao was Duke of Jin (晉公) and then King of Jin (晉王) before his son Sima Yan accepted the Wei emperor’s abdication and founded the Jin dynasty. The title of duke was thus a key stage in the transition from Han to Wei and from Wei to Jin.