Complex sentence: His involvement was the re-education of captured Japanese soldiers, and psychological warfare against the Empire of Japan for the Kuomintang in the wartime capital of Chongqing which was conducted by the Japanese People's Anti-War Alliance (Hansen Domei).
Split into simpler sentences: His involvement was the re-education of captured Japanese soldiers, and psychological warfare against the Empire of Japan for the Kuomintang in the wartime capital of Chongqing. He was involved with the Japanese People's Anti-War Alliance (Hansen Domei).