The Qing forces were initially defeated by Wu in 1673-1674. Manchu Generals and Bannermen were put to shame by the performance of the Han Chinese Green Standard Army, who fought better than them against the rebels. The Qing had the support of the majority of Han Chinese soldiers and the Han elite, as they did not join the Three Feudatories. Different sources offer different account of the Han and Manchu forces deployed against the rebels. According to one, 400,000 Green Standard Army soldiers and 150,000 Bannermen served on the Qing side during the war. according to another, 213 Han Chinese Banner companies, and 527 companies of Mongol and Manchu Banners were mobilized by the Qing. According to a third, mustered the Qing a massive army of more than 900,000 Han Chinese to fight the Three Feudatories. Fighting in northwestern China against Wang Fuchen, the Qing put Bannermen in the rear as reserves while they used Han Chinese Green Standard Army soldiers and Han Chinese Generals like Zhang Liangdong, Wang Jinbao, and Zhang Yong as their main military force. The Qing thought that Han Chinese soldiers were superior at fighting other Han people and so used the Green Standard Army as their main army against the rebels instead of Bannermen. As a result, after 1676, the tide turned in favor of the Qing forces. In the northwest, Wang Fuchen surrendered after a three-year-long stalemate, while Geng Jingzhong and Shang Zhixin surrendered in turn as their forces weakened.
Question: How many years did it take Qing forces to defeat Wu?
Answer: 1