United States Special Forces have established a well-deserved reputation as experts in direct action operations to kill or capture high-value targets over the course of the Global War on Terror. In doing so, they have neglected their core mission of unconventional warfare. This book uses history, theory, and doctrine to study the successful guerrilla operations conducted in the Philippines against occupying Japanese forces and provides lessons in motivating individuals or groups to join or support guerrilla movements that can be applied to current or future unconventional warfare scenarios to support United States' operational objectives. This book begins with an overview of theories of cooperation and resistance that describe common factors that motivate and deter people from joining or supporting guerrilla groups. These factors are then compared with successful and unsuccessful attempts to build a resistance movement using case studies taken from the Philippine Islands during World War II. Finally, the historical record is compared to current United States policy and doctrine for unconventional warfare to explain the importance of gaining support for resistance movements and ways in which unconventional warfare can compliment conventional campaigns.