Gause sees the three big states of Iran, Iraq, and Saudi Arabia, together with the small states of Bahrain, Kuwait, Oman, Qatar, and the United Arab Emirates, as forming a distinct system of international relations in which the foreign policy of each country is shaped largely by its relations with the others (plus its relationship with a dominant outside actor). He demonstrates the workings of this distinctive system from the early 1970s to the present. Given that these four decades witnessed the British withdrawal from the Persian Gulf, the United States' ever-increasing involvement, the rise of Iran, and three wars, simply producing a clear and coherent account of the system at work would be an achievement. Gause accomplishes this and more. His organizing theme is the concern of all Persian Gulf states, great and small, for regime security, but he also treats other matters, from the role of oil to transnational issues. A long chapter that examines why the United States invaded Iraq in 2003 shows the strength of this book: with his deep knowledge of the region, careful scholarship, and judicious attitude, Gause offers consistently sound interpretations.