Since the end of World War II, there have been nearly one-hundred insurgencies of significant size, many of which featured interventions by third-party military forces. While many theories contribute to an explanation of why a government wins or loses a war, there is insufficient understanding of the role intervener commitment plays in the outcome. This monograph examines the mechanisms that translate an intervener's commitment into success or failure. This question is particularly salient to the United States, which has been a party to insurgencies in Afghanistan and Iraq for the better part of a decade. Furthermore, nearly every strategy document published since the beginning of these wars points to a future in which the American military and its allies remain engaged in insurgencies around the globe. When a third-party intervenes militarily in an insurgency on the side of the government, success is more likely when its commitment is understood in terms of resource levels. When the intervention is on the side of the insurgents, success is more likely when the intervener commits to defeating the incumbent government. Put another way, the level of commitment can be conceptualized as a choice between helping the favored side win at all reasonable costs or to offer qualified support with defined limits. The latter is the more prudent approach when backing a government in the role of counterinsurgent. While an actual intervention will likely take on some dynamic combination of these two poles as it unfolds over time, the choices a third party makes persist along this continuum. It is important that the intervener consider its overall type of commitment and strategy for communicating that commitment, since these choices will engender different reactions from both the insurgent and counterinsurgent. Interventions can increase or decrease the aggressiveness of both sides of an insurgency. While the obvious preference is to increase the aggressiveness of the favored side while decreasing that of the opposition, interveners may find that their strategic choices work at cross purposes, driving both sides to move in the same direction, though at different intensities. Choosing an appropriate strategy for intervention - and not simply deciding on the operational techniques the intervener will use to execute the intervention - significantly affects the implementers of policy, military or otherwise. Most importantly, the decision affects the prospects for success or failure, regardless of whether the intervener is supporting the insurgents or the counterinsurgents. Choosing the appropriate type of commitment and effectively communicating it to all parties becomes perhaps as important as the specific ways and means employed in execution of that strategy.

ADA 523117 Approved for public release; distribution is unlimited. The opinions and conclusions expressed herein are those of the student-authors and do not necessarily represent the views of the U.S. Army Command and General Staff College or any other governmental agency. (References to these studies should include the foregoing statement.)