This book explores the methods employed by the underground resistance movements of World War II to manage the inherent difficulties associated with operating in a clandestine environment. Specifically, it examines the role of the underground. The advantages and disadvantages of operating underground, and the management procedures implemented by the clandestine organizations developed to manage problems of recruitment, internal security, leadership and command and control, The "underground" is examined generically, recognizing that there are fundamental operating principles, management requirements, and security dictates that are universally applicable -- whether discussing World War II resistance movements or contemporary guerrilla groups.