In January 1980,U.S. President Jimmy Carter used his State of the Union address to announce that in order to protect "the free movement of Middle East oil," the United States would repel "an attempt by any outside force to gain control of the Persian Gulf." Carter and his successors made good on that pledge, ramping up U.S. military capabilities in the region and even fighting the Gulf War to prevent Saddam Hussein's Iraq from dominating the region's oil supplies. Although Washington has had a number of interests in the Persian Gulf over the years, including preventing nuclear proliferation, fighting terrorism, and spreading democracy, the main rationale for its involvement has always been to keep the oil flowing...