Interstate conflict, in the view of one-third of the global decision-makers and experts assembled to compile the World Economic Forum 2015 Global Risks Report, was the most probable serious danger facing the East Asia-Pacific region over the coming decade.1 A Pew Research Center global opinion poll conducted in the spring of 2014 found that people in eight of the 11 Asian countries surveyed expressed fears about possible military conflict over territorial disputes involving the People’s Republic of China and its neighbors. In China itself, more than six in every ten citizens expressed similar concerns. Two-thirds of Americans in 2014 also feared that intensifying territorial disputes between China and its neighbors could spark an armed conflict.2 Although the World Economic Forum 2017 Global Risks Report considered such conflict as a decreasing risk in terms of likelihood and impact,3 majorities in China, Japan and several other East Asian nations remained concerned about territorial tensions and the strategic drama being played out between the United States and China on land and at sea across the region had begun to fuel fears that the “Pacific century” might be shattered by a new Pacific war.4 For better or for worse, Southeast Asia, the region which has given birth to the most vigorous efforts to construct a regional security architecture designed to ensure long-term peace and stability in Asia and the wider Pacific Basin, is today confronted by a series of intractable problems that may well constitute the greatest tests it has faced since the end of the Cold War. Much has been said about the significance of the South China Sea for the security and development of the Indo-Pacific. This sea offers the shortest route from the Pacific Ocean to the Indian Ocean. About half of the world’s commerce, half of global liquefied natural gas and a third of global crude oil transit through this body of water each year.5 Two-fifths of the world’s tuna are born in the South China Sea, contributing to a multibillion-dollar fisheries industry.6 These statistics, oft-cited, are just a few indicators of the South China Sea’s importance to the region and the world at large. A durable regional security system that can deliver lasting stability and prosperity for the Indo-Pacific cannot be constructed in the absence of a smoothly functioning regional maritime order in this critical area. Yet this body of water, blessed with so many valuable resources and crisscrossed by a network of vital sea-lanes, has become the home to some of the most intractable territorial disputes in Asia and a stage for intensifying great power strategic competition. The longstanding territorial and maritime disputes simmering in the South China Sea and the machinations of great powers have been slowing down the momentum for regional cooperation and frustrating attempts to forge a robust and mutually beneficial security architecture. There is also another troubling dimension of very great significance. While the tempo of regional cooperation has slackened, the rate at which the South China Sea marine environment is deteriorating has accelerated. Forty percent of the South China Sea’s fish stocks have already been exhausted and, according to the United Nations Food and Agriculture Organization, most fish resources in the western part of the South China Sea have been exploited or overexploited.7 Meanwhile, 70 percent of the South China Sea’s coral reefs are reported to be in poor or only fair condition.8 Put simply, while the challenges to the South China Sea marine environment are growing, the capacity of regional mechanisms to effectively address those challenges has been undermined or severely constrained.