It brought Indonesia into co-operative relations with its neighbouts, and it sidelined differences among its members so that outsiders could not exploit them.
ASEAN was a brilliant success in achieving its initial aim―to nurture regional security by bringing Indonesia, the largest of the Southeast Asian states, into a co- operative security relations with its neighbouts. Indonesia's "national resilience" was also critical to regional stability, since in the 1950s and 1960s Indonesia's domestic turmoil had attracted the competitive interest of the great powers.
After the coming to power of Suharto's New Order in 1966 made ASEAN possible, the ASEAN countries received sotto voce a great deal of external support from the West. Not surprisingly, since four of the five founding members hosted Western bases. Enlightened self-interest worked both ways. By helping to secure the Southeast Asian straits, ASEAN contributed greatly to regional and global security.
ASEAN's second main achievement has been to quarantine differences among its members, thus preventing potentially hostile external powers from exploiting such tensions. The extent of intramural differences based on ethnicity and religion makes ASEAN's achievements even more remarkable. Many territorial and other disputes exist, but have been set aside. Indonesia and Malaysia, for example, were unable to resolve their dispute over some islands off Borneo, but have sent it to the International Court of Justice.
No more 'applied realpolitik'
In the 1980s, ASEAN resisted when Vietnam invaded Cambodia with Soviet backing. ASEAN could do so because it enjoyed the combined support of the United States and China, which had moved into de facto alliance in order to oppose Soviet hegemony. ASEAN understood that the vital interests of one of its members, Thailand, was at stake. So it coordinated resistance to Vietnam, demonstrating its capacity to cooperate in spite of real differences.
That was especially hard for Indonesia, given its fears of China, doubts about Thai resilience, and propensity to see Vietnam as a natural ally against China. Yet Indonesia went along with Thailand's entering into de facto alliance with China, including an arms supply relationship. Vietnam's withdrawal from Cambodia in 1990 was finally brought about by US-China strategic co-operation and the ending of Soviet backing for Vietnam, in regional counterpoint to the liquidation of the Cold War.
