The U.S. military is first-rate, yet it struggles to fight and win irregular wars. Surprisingly, throughout the course of history great powers have had difficulty with small wars. One must ask then, why and how do irregulars win as often as they do? The answer to this question will enable the United States to support irregulars more effectively, and defeat irregulars more efficiently. This thesis considers seventeen irregular conflicts between WWII and the present day to determine why irregulars win when they do, and how asymmetries of motivation can affect the outcome of irregular wars. A mixed methodology, including heuristics, process tracing, and comparison of case studies is used to evaluate irregular wars and the motivations of the combatants. The findings suggest that asymmetries of motivation only partially explain why irregulars succeed. Irregulars can succeed when motivations are symmetric as well as asymmetric. Internal conflicts that exhibited symmetrical motivation were often long, bloody, and costly affairs resolved primarily by negotiations. Alternatively, when asymmetries of motivation have existed, the weak were able to influence intrinsic and extrinsic motivations to coerce their adversaries to quit. Ultimately, the findings from this thesis indicate that opinion and public support significantly influence an actors motivation and will to fight. In light of this, this thesis suggests that SOF should focus on advising irregulars to shape opinions and perceptions to undermine their opponents will to fight. Furthermore, the U.S. government should focus more on the application of political and psychological warfare to enable U.S. SOF operations in support of both counterinsurgency and unconventional warfare operations.