This book offers an analysis of the four central regional security themes relevant to the policy-focussed discussions at the annual IISS Shangri-La Dialogue. Namely: The evolving roles of the United States and China in Asia-Pacific security;Responses by the US and regional states to regional security tensions, particularly in the South China Sea;Emerging security questions relating to nuclear weapons, missiles and military cyber capabilities;The prospects for regional security cooperation, including the challenges for the ASEAN-centred architecture.