While policy makers and scholars have long devoted considerable attention to strategies like deterrence, which threaten others with unacceptable consequences, such threat-based strategies are not always the best option. In some cases, a state may be better off seeking to give others a greater sense of security, rather than by holding their security at risk. The most prominent use of these security assurances has been in conjunction with efforts to prevent the spread of nuclear weapons. Ongoing concerns about the nuclear activities of countries like Iran and North Korea, and the possible...