It is a sign of the times that Tierney’s brave and interesting book begins with the assumption that most contemporary wars are essentially unwinnable for the United States. This is because they are civil conflicts rather than interstate wars. The United States tends to find itself in uncomfortable positions when intervening in such conflicts, quickly looking for a way out; indigenous forces, by contrast, often know how to play the long game required by such situations. The simplest way to avoid unwinnable wars is not to engage in them in the first place, but Tierney is not sure it will always be possible for Washington to stay out. If intervention becomes necessary, Tierney urges U.S. officials to think carefully about the difficult security challenges that arise even after relatively easy initial combat successes and to remember the importance of a credible exit strategy. Tierney’s argument is imaginatively organized around a sequence he dubs “surge, talk, and leave”: strengthening one’s position before engaging in negotiations that might allow for a dignified departure.