The Qing forces were crushed by Wu from 1673-1674. The Qing had the support of the majority of Han Chinese soldiers and Han elite against the Three Feudatories, since they refused to join Wu Sangui in the revolt, while the Eight Banners and Manchu officers fared poorly against Wu Sangui, so the Qing responded with using a massive army of more than 900,000 Han Chinese (non-Banner) instead of the Eight Banners, to fight and crush the Three Feudatories. Wu Sangui's forces were crushed by the Green Standard Army, made out of defected Ming soldiers.
What happened to Wu's army?
crushed by the Green Standard Army