The Association of Southeast Asian Nations (ASEAN) is celebrating its 40th anniversary this year. Uniting the 10 major mainland and insular Southeast Asian states, ASEAN has also established formal links to Northeast Asia (ASEAN+3), as well as to the world at large (ASEAN Regional Forum). It is appropriate at this time to take stock of ASEAN and project its future. How effectively have ASEAN and its organizational offspring functioned as a security community? Have the Association's members been able to aggregate their security interests? Have they presented a united security front to other states? Do they collaborate to resolve internal security problems and protect one another against external security challenges? In this monograph, Professor Sheldon Simon, who has written on Asian security for over 40 years, argues that ASEAN is pursuing an engagement strategy in the 21st century, bringing the great powers (the United States, China, India, Japan, and the European Union) into Southeast Asia's political...