International Law and the Common Knowledge Requirements of Cross-Domain Deterrence

The complexity of cross-domain deterrence is a major barrier to establishing coordinated expectations about violations and consequences. For a system of cross-domain deterrence to work, actors must understand what actions will trigger a response, what the response is likely to be, and how willing the respondent is to act. Any such system is likely to be less robust than Cold War nuclear deterrence because of the number of domains involved, constraints on revealing secret capabilities or even the identity of the challenger, and a propensity for provocations that fall below the established threshold of response. This chapter recommends using an analogy to the law of war rather than to nuclear deterrence to understand the possibilities of setting up a workable regime of cross-domain deterrence, even as the author is pessimistic about the ability of any collective regime to adequately manage the complexity of cross-domain deterrence.