Emperor Xian of Han
In 220, Emperor Xian of Han formally abdicated the imperial throne to Cao Pi, who then became the founding emperor of the Wei dynasty. This succession reflected the political reality of Cao Wei control over the imperial court as well as the majority of economic and demographic resources in China, and satisfied propriety through the ritual abdication ceremony. Since the time of Chen Shou, who compiled his massive "Records of the Three Kingdoms" sometime in the 280s or 290s, historians had treated the Wei dynasty as the legitimate as well as "de facto" successors to the Han, in part because the ruling Jin dynasty partially derived its legitimacy through a smooth transfer of the mandate through Wei. Xi Zuochi put forth an alternative judgment, stating that as Wei neither controlled the whole of China nor had imperial blood in its ruling house, it should be considered an illegitimate dynasty, no better than the Xin Dynasty of Wang Mang. According to Xi Zuochi's biography in the "Book of Jin", he formulated his theory of dynastic legitimation in the "Annals of Han and Jin" (漢晉春秋 "Han Jin Chun Qiu") in order to curb and correct his overambitious patron, Huan Wen.