The decision by the Association of Southeast Asian Nations (ASEAN) Defence Ministers' Meeting-Plus (ADMM-Plus) in Malaysia in November 2015 to scrap a planned joint statement on the South China Sea issue was a stark reminder of the persistent differences among some of its member states. The ADMM-Plus is made up of the ten ASEAN countries and Australia, China, India, Japan, New Zealand, Russia, South Korea, and the United States. The failure to agree on a statement fostered the impression that the ADMM-Plus could go the way of the ASEAN Regional Forum (ARF), an older and more established regional experiment in security cooperation that many today feel has grown moribund.1 Moreover, despite the decision by the ADMM-Plus to conduct its ministerial gatherings on a biennial rather than triennial basis, some pundits warn of the risk that the ADMM-Plus will end up as a talk shop that achieves little real progress.2But for the officials and military practitioners who make the ADMM-Plus tick, nothing could be further from the truth. Since the inaugural ADMM-Plus in Vietnam in 2010, joint military exercises involving the grouping's eighteen member countries have grown in frequency and complexity. Working groups set up in areas such as counterterrorism, humanitarian assistance and disaster relief (HADR), maritime security, military medicine, peacekeeping, and de-mining have started to bear fruit, albeit in certain areas more than in others. That said, despite its impressive accomplishments in practical collaboration-indeed, the ADMM-Plus has gone further than any existing regional cooperative framework-there are questions concerning how effective the ADMM-Plus can truly be as a mechanism for mitigating tensions and alleviating the trust deficits that have come to define interstate relations today in hotspots like the South China Sea.ASEAN Defense Cooperation before the ADMM-PlusSince the 1970s, if not earlier, the ASEAN countries have had no qualms about exploiting the space between collective and nonsecurity-oriented regionalism through bilateral security cooperation with one another, such as via border security agreements and intelligence exchanges. During the 1980s, Singapore's prime minister, Lee Kuan Yew, proposed the idea of a trilateral or even quadrilateral arrangement, which was roundly rejected by his ASEAN counterparts. Subsequent calls were rendered by the Indonesian and Malaysia foreign ministers, Mochtar Kusumaatmadja and Abu Hassan Omar, for an ASEAN military arrangement and community, respectively.3 By 1989, bilateral military exercises between the so-called core ASEAN states-Indonesia, Malaysia, and Singapore-had become sufficiently thick as to merit being described by Indonesian vice president Try Sutrisno as a defense spider web. 4At its summit in Singapore in 1992, ASEAN formally included security issues in its agenda. By the mid-1990s, trilateral cooperation involving Indonesia, Malaysia, and Singapore had become relatively commonplace. The establishment of the ARF in 1994 paved the way for regular consultation among Asia-Pacific officials and practitioners through mechanisms such as the ARF Defence Officials' Dialogue and the ARF Security Policy Conference. Beyond the formal auspices of ASEAN, various military-to-military interactions and activities that have been regularized include the ASEAN Chiefs of Defence Forces Informal Meeting, the ASEAN Chiefs of Army Multilateral Meeting, the ASEAN Navy Interaction, the ASEAN Air Force Chiefs Conference, the ASEAN Military Intelligence Meeting, and the ASEAN Armies Rifles Meet. The Western Pacific Naval Symposium, formed in 1988, also deserves mention. In 2014 in Qingdao, the fourteenth symposium endorsed the establishment of a Code for Unplanned Encounters at Sea (CUES), a nonbinding pact for avoiding incidents at sea between countries and preventing those that do occur from escalating. …