The US faces major challenges in dealing with Iran, the threat of terrorism, and the tide of political instability in the Arabian Peninsula. The presence of some of the world’s largest reserves of oil and natural gas, vital shipping lanes, and Shia populations throughout the region have made the peninsula the focal point of US and Iranian strategic competition. Moreover, large youth populations, high unemployment rates, and political systems with highly centralized power bases have posed other economic, political, and security challenges that the GCC states must address, and which the US must take into consideration when forming strategy and policy. An updated study by the CSIS Burke Chair explores US and Iranian interests in the region, Gulf state and GCC policies toward both the US and Iran, and potential flash-points and vulnerabilities in the Gulf to enhanced competition with Iran. This study examines the growing US security partnership with Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the UAE – established as the Gulf Cooperation Council (GCC). It analyzes the steady growth in this partnership that has led to over $64 billion in new US arms transfer agreements during 2008-2011. It also examines the strengths and weaknesses of the security cooperation between the southern Gulf states, and their relative level of political, social, and economic stability. The study focuses on the need for enhanced unity and security cooperation between the individual Gulf states. It finds that such progress is critical if they are to provide effective deterrence and defense against Iran, improve their counterterrorism capabilities, and enhance other aspects of their internal security.