There has been a dramatic unconventional warfare (UW) renaissance in recent years. Much of the published material on the subject has been focused on what unconventional warfare is, re-defining it, and attempting to frame the concept of its use as it relates to the current military operational environment. Little work has been produced that examines the more basic question: Why UW? This research begins where the 2009 redefinition of UW left off. Identifying an expanded field of 51 cases of U.S.-sponsored unconventional warfare from 1892 to 2010, the authors select four cases that represent a wide variety of UW methods, locations, and goals. These four cases of UW are compared with one case of conventional warfare focusing on the question: What are the factors that lead to the use of unconventional warfare as a strategic policy option? This study empirically identifies what factors lead to the use of unconventional warfare. The results of this study provide recommendations for the advancement of UW as a strategic option. By understanding the why first, as in why unconventional warfare is chosen as a method of operation, the subsequent questions of how and who become easier to answer.