The GCC, made up of Saudi Arabia, Bahrain, Kuwait, Oman, Qatar and the UAE, is one of the most resilient sub-regional organizations in the world, and the most successful in the one in the Arab world. It has been the forum through which much internal security co-operation in this volatile sub-region has taken place, as well as the main representative for the UAE's territorial dispute with Iran over the Aub Musa and Tunbs Islands. It also has significant potential to present an alternative form of leverage over the international oil markets. Very little is known however about how the organization really works: how decisions are actually taken, as opposed to how this process is formally constituted in its charters, and what the GCC's real impact on member states, the Gulf and international relations is. Drawing on cutting-edge IR theoretical perspectives as well as unique first-hand access to GCC decision-makers, Matteo Legrenzi explains the mechanisms of Gulf cooperation - and its limitations - in the context of economic globalisation, diplomatic regionalisation and the rise of Iran. Combining historical context, primary source investigations and theoretical analysis, it is the first comprehensive guide to the GCC and an indispensable resource for anyone concerned with the Gulf and the Middle East.