Gongsun Yuan
Although Gongsun Yuan was nominally a vassal of Cao Wei, his brief flirtation with Wu and brazen derogatory comments about Wei earned him a reputation as unreliable. From Wei's point of view, although the Xianbei insurrection by Kebineng had been put down recently, Liaodong's position as a buffer zone against barbarian invasions needed to be clarified. Therefore, it was clearly unacceptable that its leader, Gongsun Yuan, was of questionable loyalty. In 237, Guanqiu Jian presented a plan to invade Liaodong to the Wei imperial court and put his plan into action. With troops of You Province as well as Wuhuan and Xianbei auxiliaries, Guanqiu Jian crossed the Liao River east into Gongsun Yuan's territory and clashed with his enemy in Liaosui (遼隧; near present-day Haicheng, Liaoning). There the Wei forces suffered a defeat, and were forced to retreat due to the floods caused by the summer monsoon season.