As Regent
Also in spring 547, Hou Jing, unsure whether Gao Huan was still alive but believing that Gao Huan had died, rebelled, first surrendering the 13 provinces he commanded to Western Wei, and then to Liang Dynasty. Gao Cheng initially sent Han Gui (韓軌) against Hou, and Han had some successes against Hou's forces, but was forced to withdraw when Western Wei forces arrived, taking four of Hou's provinces in exchange for supporting Hou. Subsequently, Hou broke with Western Wei, and Western Wei forces withdrew. Meanwhile, Emperor Wu of Liang commissioned his nephew Xiao Yuanming the Marquess of Zhenyang with a large force to try to aid Hou. Gao Cheng, after finally revealing Gao Huan's death, put Murong Shaozong in charge of the army. He also made peace overtures to Hou, promising to keep him in command of the southern provinces if he would submit. Hou refused.
Meanwhile, Gao Cheng also had a threat from within. Gao Cheng, once Gao Huan died, began to show contempt for Emperor Xiaojing, and once, when Emperor Xiaojing rebuked him for public disrespect, Gao Cheng ordered Cui Jishu to punch Emperor Xiaojing three times. Emperor Xiaojing, fearful of what might come next, formed a conspiracy against Gao Cheng. In winter 547, the plot was discovered, and Gao Cheng put the emperor under arrest and executed his coconspirators.
Late in 547, Murong Shaozong crushed Xiao Yuanming's army at Hanshan (寒山, in modern Xuzhou, Jiangsu), capturing Xiao Yuanming. When Xiao Yuanming was delivered to Gao Cheng, Gao Cheng treatedly him with respect, intending to try to use Xiao Yuanming as a pawn against Hou. By spring 548, Murong Shaozong had crushed Hou's army as well, and Hou fled to Liang, seizing the Liang border city of Shouyang (壽陽, in modern Lu'an, Anhui) as his base of operations. Gao Cheng then began negotiating peace with Liang's Emperor Wu, intending to create instability in the relationship between Emperor Wu and Hou. Hou, eventually coming to believe that Emperor Wu would betray him and turn him over to Eastern Wu to exchange for Xiao Yuanming, rebelled in fall 548, eventually capturing the Liang capital Jiankang and holding Emperor Wu and then his successor Emperor Jianwen of Liang as puppets. Once Hou did so, he made an overture of peace to Gao Cheng, but Gao Cheng did not respond.
Meanwhile, Gao Cheng was trying to recapture the provinces that Western Wei had taken from Hou. Also in 548, he sent Gao Yue and Murong Shaozong to siege Changshe (長社, in modern Xuchang, Henan), but Changshe, defended by the Western Wei general Wang Sizheng (王思政), would not fall easily, and during the battle, Western Wei forces were able to kill Murong Shaozong and another major general, Liu Fengsheng (劉豐生). In summer 549, Gao Cheng himself commanded reinforcements and arrived at Changshe. He intensified the siege, and soon, Changshe fell, and he captured Wang, whom he treated with respect. After Changshe fell, Western Wei forces also withdrew from the three other provinces that they had captured, and Eastern Wei by this time had recaptured all of the land that Hou had initially taken.
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