Cao Yu
In 232, during the reign of Cao Rui (Cao Pi's son and successor), Cao Yu's title was changed to "Prince of Yan" (燕王). Cao Rui had been very close to Cao Yu in his childhood and he favoured the latter, so he treated Cao Yu exceptionally after ascending the throne in 226 upon his father's death. In 235, Cao Yu was summoned to serve in the Wei imperial court. He returned to Ye (鄴; in present-day Handan, Hebei) in 237, but was summoned back to the Wei capital Luoyang in the summer of 238. Cao Rui became seriously ill in the winter of 238–239 and he appointed Cao Yu as General-in-Chief (大將軍) in the hope that Cao Yu would assist his successor in governing the state. After serving as General-in-Chief for a few days, Cao Yu had the intention of resigning. At the same time, Cao Rui had also changed his mind so he relieved Cao Yu of his duty. Cao Yu returned to Ye in the summer of 239 after Cao Rui's death.