Insurgencies have dominated the focus of the U.S. military for the past seven years, but they have a much longer history than that and are likely to figure prominently in future U.S. military operations. Thus, the general characteristics of insurgencies and, more important, how they end are of great interest to U.S. policymakers. This study constitutes the unclassified portion of a two-part study that examines insurgencies in great detail. The research documented in this monograph focuses on insurgency endings generally. Its findings are based on a quantitative examination of 89 cases.

An analysis of insurgent warfare, looking at factors that contribute to insurgency.

The result of a multiyear project spearheaded by the late Marianne Heiberg, "Terror, Insurgency, and the State" assembles the findings of more than a dozen scholars who have conducted extensive field research with rebel groups. This comparative analysis documents the aim of longstanding insurgent groups.

RAND studied 89 modern insurgency cases to test conventional understanding about how insurgencies end. Findings relevant to policymakers and analysts include that modern insurgencies last about ten years; withdrawal of state support cripples insurgencies; civil defense forces are useful for both sides; pseudodemocracies fare poorly against insurgents; and governments win more often in the long run.

When a country is threatened by an insurgency, what efforts give its government the best chance of prevailing? Contemporary discourse on this subject is voluminous and often contentious. Advice for the counterinsurgent is often based on little more than common sense, a general understanding of history, or a handful of detailed examples, instead of a solid, systematically collected body of historical evidence. A 2010 RAND study challenged this trend with rigorous analyses of all 30 insurgencies that started and ended between 1978 and 2008. This update to that original study expanded the data set, adding 41 new cases and comparing all 71 insurgencies begun and completed worldwide since World War II. With many more cases to compare, the study was able to more rigorously test the previous findings and address critical questions that the earlier study could not. For example, it could examine the approaches that led counterinsurgency forces to prevail when an external actor was involved in the conflict. It was also able to address questions about timing and duration, such as which factors affect the duration of insurgencies and the durability of the resulting peace, as well as how long historical counterinsurgency forces had to engage in effective practices before they won.

The most useful forms of outside support for an insurgent movement include safe havens, financial support, political backing, and direct military assistance. Because states are able to provide all of these types of assistance, their support has had a profound impact on the effectiveness of many rebel movements since the end of the Cold War. However, state support is no longer the only, or indeed necessarily the most important, game in town. Diasporas have played a particularly important role in sustaining several strong insurgencies. More rarely, refugees, guerrilla groups, or other types of non-state supporters play a significant role in creating or sustaining an insurgency, offering fighters, training, or other forms of assistance. This report assesses post-Cold War trends in external support for insurgent movements. It describes the frequency that states, diasporas, refugees, and other non-state actors back guerrilla movements. It also assesses the motivations of these actors and which types of support matter most. This book concludes by assessing the implications for analysts of insurgent movements.