This paper examines one method to measure the willingness of nations to take risks in international conflicts. Because war is inherently risky, the willingness to take risks is one of the most important predictors of escalation. This paper examines alliance behavior to find a measure for national risk attitudes. The willingness to take risks is identified with the trade-off between autonomy and security expressed in a nation's alliances. Two rational-choice models, one for alliance behavior and one for war decisions, are linked to create this identification. Formally, the odds of the break-even probability of success that a nation will accept for a given war equal its marginal rate of substitution between autonomy and security. Finally, the strengths and weaknesses of one existing measure of national risk attitudes are analyzed in light of the argument.