Complex sentence: Wataru Kaji, a Japanese dissident who, prior to his arrival in China in 1936, was persecuted in Imperial Japan for his political activity, joined the Kuomintang, where he was attached to the propaganda section of the Chinese Army Political Department.
Split into simpler sentences: Wataru Kaji, a Japanese dissident who, prior to his arrival in China in 1936, was persecuted in Imperial Japan for his political activity, joined the Kuomintang. He was attached to the propaganda section of the Chinese Army Political Department.