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During a war against Zhang Zuolin in October 1924, Cao was betrayed and imprisoned by one of his own officers, General Feng Yuxiang, in the Beijing coup. Feng occupied Beijing and forced Cao to resign. His brother, Cao Rui, committed suicide while he was under house arrest. In 1926, Cao Kun was released from captivity as a goodwill gesture by Feng to Wu Peifu.