The contention over the quantity and quality of regional missile defenses forward-deployed by the United States in the Asia-Pacific region animates much of the US–China disagreement about strategic stability. The Chinese argue that the deployed assets exceed reasonable defensive requirements and suggest that if these missile-defense deployments continue, they will be forced to increase the size of their nuclear arsenal. In disagreement, the United States claims that regional missile defenses are defensive by design, limited in scope, and necessary to defeat a North Korean missile campaign. In this article, a series of simulation experiments were developed to empirically test these opposing arguments over missile defenses and strategic stability. The simulations indicate that current deployments are necessary for defense and proportional to the threat. The analysis also argues that current deployments do not possess the ability to alter the US–China strategic nuclear balance significantly. The article concludes with a discussion of other subjective aspects of national security that may explain Chinese concerns and explore possible ways to reassure China.