The U.S. Army Guerrilla Warfare Handbook, historically linked to doctrines like Field Manual 31-21, serves as a foundation for unconventional warfare, focusing on organizing resistance within denied areas during the Cold War. It emphasizes building local support, maintaining operational security, and leveraging small-unit tactics to transition from clandestine operations to organized military action against a conventional force. You can find detailed historical analyses of these military manuals through public military history archives.