Provocations by North Korea can take various forms: weapons tests, acts of direct violence, cyber attacks, threatening force buildups, etc. Individually and as a group, states are debating how they would respond to one or another of these actions. In Section IV, authors evaluate how four states on the frontlines assess the options available to them in response. We start with South Korea, the most likely target of a provocation. Then, we turn to the United States, which is committed by alliance and retains operation command of joint forces in time of war in Korea. Third, coverage turns to Japan, also under threat but likely to prepare for only an indirect role unless it is attacked. Finally, our attention shifts to China, which is raising questions about what actually constitutes a provocation. Missing in the set of papers is Russia, which is discussed briefly later in this introduction. As many await new North Korean challenges, which will be viewed as provocations in at least three states, comparing the military responses that are being planned warrants close attention. Diplomatic and economic responses are set aside here in order to focus on military responses.