Despite a U.S. focus on securing an international deal to curb Iran's nuclear development for the last several years, the United States lacks a strategy to combat the full range of Iranian activities that threaten the interests of the United States and its allies but fall short of conventional warfare. In this report, CSIS's International Security Program sets forth analysis of Iran's strategy, motivations, military, and paramilitary capabilities and evaluates the effects of Iranian behavior on key U.S. partners. The study leverages the expertise of contributing authors at CSIS, the American Enterprise Institute, the Center for Naval Analyses, the Washington Institute for Near East Policy, Harvard University and the University of Hawaii to inform its analysis. The study proposes a framework for deterring Iran, including practical recommendations for the U.S. administration and Congress that would enhance the security of the United States and its allies and partners.