American history is replete with instances of counterinsurgency. An unsurprising reality considering the United States has always participated in empire building, thus the need to pacify resistance to expansion. For much of its existence, the U.S. has relied on its Army to pacify insurgents. While the U.S. Army used traditional military formations and use of technology to battle peer enemies, the same strategy did not succeed against opponents who relied on speed and surprise. Indeed, in several instances, insurgents sought to fight the U.S. Army on terms that rendered superior manpower and technology irrelevant. By introducing counterinsurgency as a strategy, the U.S. Army attempted to identify and neutralize insurgents and the infrastructure that supported them. Discussions of counterinsurgency include complex terms, thus readers are provided with simplified, yet accurate definitions and explanations. Moreover, understanding the relevant terms provided continuity between conflicts. While certain counterinsurgency measures worked during the American Civil War, the Indian Wars, and in the Philippines, the concept failed during the Vietnam War. The complexities of counterinsurgency require readers to familiarize themselves with its history, relevant scholarship, and terminology—in particular, counterinsurgency, pacification, and infrastructure.