The Rational Timing of Surprise

National leaders are frequently surprised by the actions of other governments. This paper explores the structure common to problems involving the use of resources for achieving surprise. Such resources include deception through double agents and through sudden changes in standard operating procedures. Still other resources for surprise include cracked codes, spies, and new weapons. Since surprise is usually possible only by risking the revelation of the means of surprise, in each case the same problem arises: when should the resource be risked and when should it be maintained for a potentially more important event later? A rational-actor model is developed to provide a prescriptive answer to this question. Examining the ways in which actual actors are likely to differ from rational actors leads to several important policy implications. One is that leaders may tend to be overconfident in their ability to predict the actions of their potential opponents just when the stakes get large. Another implication is that, as observational technology improves, the potential for surprise and deception may actually increase.