Governments do not like being caught by surprise, but it happens all the time, leaving them looking foolish when they fail to anticipate events that challenge the foundations of their policies. Oppenheimer believes he has a remedy for this problem. He does not try to forecast the future; instead, he constructs detailed scenarios that could plausibly take shape, by starting with what is known about the current situation and then imagining different ways in which events and decisions might unfold. Oppenheimer explains his methodology and details a number of scenarios he developed in the recent past for countries such as China, Russia, Syria, and Ukraine. These illustrate the value of the exercise but also, as Oppenheimer acknowledges, its limits. The scenarios reveal more about what was known and understood at the time that Oppenheimer drew them than about what actually happened. Oppenheimer makes a persuasive case that scenario planning can encourage more agility and flexibility in policymaking. He also presents a scathing indictment of U.S. grand strategy—but his proposed remedies for it are not convincing.