The core of this book examines the organizational structure of Japanese intelligence during WWII, and how Japan's various military branches employed individuals who could duplicate the broad clandestine functions of the historical ninja. Their ninjutsu-based activities came under the purview of the Army Intelligence Service and a special branch known as the Tokumu Kikan. Like the ninja operatives of Japan's feudal past, Tokumu Kikan agents were specially chosen, professionally trained, and liberally deployed to conduct plain-clothed acts of subversion, disinformation, espionage, sabotage, and assassination throughout the Far East. The strategies and skills they used made them Japan's de facto ninja during the first half of the 20th century.