Complex sentence: During the Battle of Shanghai he was one of the top military assistant of Chiang Kai Shek, it was his idea to seek a decisive action in the south rather than confront the Japanese in Northern China where nationalist troops were in poor condition and lacking transporting vehicles.
Split into simpler sentences: During the Battle of Shanghai he was one of the top military assistants of Chiang Kai Shek. It was his idea to seek a decisive action in the south rather than confront the Japanese in Northern China where nationalist troops were in poor condition and lacked transporting vehicles.