Who is Yangawa Heisuke from The Rape of Nanking and what is their importance?

As one of the leaders of the Japanese invasion, Yangawa Heisuke's life is shrouded in mystery. Yanagawa was a man of mystery, and there is a surprising lack of any information about his achievements or duties during the war. His photograph is missing from most wartime photos, and there appears to be no further record of his direction of troops. After the war, he died of a heart attack, thereby avoiding any fallout from his crimes during the war.