Complex sentence: Some time later, he went to Chongqing, which served as the wartime capital for the Kuomintang Republic of China government during the Second Sino-Japanese War, where he joined the Mongolian and Tibetan Affairs Commission of the Republic of China government.
Split into simpler sentences: Some time later, he went to Chongqing, which served as the wartime capital for the Kuomintang Republic of China government during the Second Sino-Japanese War. He joined the Mongolian and Tibetan Affairs Commission of the Republic of China government.