Even though security is the foundation upon which all other aspects of a peace mission must build, peace operations have routinely been plagued by serious gaps in public security. There are three distinct aspects to this public security challenge: • A Deployment Gap • An Enforcement Gap, and • An Institutional Sustainability Gap To address these gaps requires robust policing organizations that are able to perform specialized missions involving disciplined group action. These capabilities are found in police units with a military structure such as the Italian Carabinieri or French Gendarmerie. Owing to the nature of the missions they perform when deployed internationally, these forces could be described as “International Stability Police Units” or ISPUs. There are a number of hurdles to be overcome before the use of International Stability Police Units to address the public security challenges of peace operations can reach its potential. Chief among these are the need for interoperability and the limited availability of such units from countries with solid democratic orientations. Accordingly this essay will address: • The nature of the public security challenges to peace operations and the relevance of International Stability Police Units for coping with them, and • Thoughts on how to develop greater international capacity to provide ISPUs.