Who is Nakajima Kesago from The Rape of Nanking and what is their importance?

As one of the leaders of the Japanese invasion, Nakajima's troop first attacked Nanking from the west, assisted by the Japanese Air Force who destroyed key bridges and railway systems. Nakajima was an ex-secret police officer of the emperor, and one the cruelest men in the war. Nakajima has been described by authors around the world as a devil, a copy of Himmler, a specialist in thought control and torture, a sadist, a beast, and a violent man.