直皖戰爭
In January 1918, during the 1st Constitutional Protection War, Wu--who had retreated from Sichuan to the Sichuan-Hubei border--attacked Shi Xingchuan and Li Tiancai's army from the west along the Yangtze. Caught between Wu and Wang Zhanyuan in the Wuhan area, Shi and Li were defeated. Hubei independent forces ceased to be a serious threat to Beiyang power in Hubei. In 1920 Wu became Military and Civil governor of Hunan. During the Zhili–Anhui War he was captured and detained as one of the Anhui clique's leaders by Wang Zhanyuan, but in 1921 he was released.