Operation Enduring Freedom and Operation Iraqi Freedom showcased the dazzling technological and professional prowess of the U.S. military in conventional operations. As more recent experience in Iraq and Afghanistan demonstrate, however, significant challenges remain in confronting protracted insurgency and instability. The way insurgents have vexed U.S. troops and civilian agencies may also embolden future opponents to embrace insurgency as the only viable means for combating the Unite States. Thus, both current and future wars demand that the U.S. improve its ability to conduct counterinsurgency (COIN) operations. Over the course of five decades, RAND has accumulated an impressive body of research on counterinsurgency, from theories of why insurgency takes place to tactical operations. The author provides an intellectual history of COIN theory, summarizes elements of successful COIN campaigns, and makes recommendations on improving it based on RAND's decades-long study of the subject. Covering a wide range of cases, from the British experience in Malaysia to the French in Algeria to the United States in El Salvador, the author points out that while specific details vary greatly, lessons of insurgency and counterinsurgency can and should be applied in Iraq, Afghanistan, and wherever else the U.S. may need to wage low-intensity conflict. On "Other War" provides an invaluable aid to understanding and developing successful responses to modern COIN challenges and should interest policymakers, decisionmakers in the armed forces, and specialists and students of military and political affairs. The term "other war," meaning pacification operations, arose in Vietnam to differentiate those operations from the "real war" of conventional search-and-destroy operations. This focus on high-intensity conflict has, perhaps ironically, resulted in such overwhelming superiority in nuclear and conventional military capability that opponents (with a few possible exceptions) are forced to embrace low intensity conflict as the only viable means of challenging the United States. In Iraq and Afghanistan, rapid and overwhelming conventional success has been countered by terrorism and insurgency. Adaptation and learning about COIN have thus become critical for the military in the 21st century.