The relationship between Thailand and Cambodia continues to deteriorate. The two countries' militaries have been trading blows since February, when a dispute over a temple erupted in armed clashes. A cease fire maintained the peace for a couple of months, but it collapsed last week. The trigger is a disputed border, but the real cause is long-standing enmity that politicians on both sides are exploiting for domestic purposes. The crisis is a test not only of the political maturity of the two countries' leadership, but of the meaning and relevance of the Association of Southeast Asian Nations (ASEAN), which is forced to stand idly by as two of its members make a mockery of the group's commitment to peaceful resolution of disputes.

The kingdoms of Thailand and Cambodia, two proud civilizations with long and rich histories, have contested for regional pre-eminence for centuries. One source of tension is the 900-year old Preah Vihear temple, which the International Court of Justice decided in 1962 was located on Cambodian territory, a ruling that inflamed nationalists in Thailand. In 2008, the United Nations declared the temple to be a World Heritage Site, a ruling that increased tensions between the two nations. While ownership of the temple may have been decided - legally at least - a 14.6-sq.-km patch of land surrounding it is still contested.

Given the sensitivity of the site, periodic clashes there are not unusual. There was fighting when Cambodia asked the U.N. to designate the temple a World Heritage Site but it was limited. This February, for reasons that are still unclear, conflict broke out for several days and ran through several cease fires. By the time the fighting stopped, 11 troops had been killed, dozens more wounded and 30,000 people had been displaced.