The world is still trying to grasp the meaning of the summit between the two Koreas. Many are euphoric; wiser heads counsel that there is a long way to go before there's real peace on the Korean Peninsula. Nonetheless, if reconciliation and, eventually, unification do come about, the effects will be felt throughout the entire region, and perhaps nowhere more strongly than in Japan.

The immediate effect of genuine peace would be a diminution of tension on the peninsula. That strikes at the heart of the rationale for a continuing U.S. military presence in South Korea. Seoul and Washington are already on the defensive. During her recent swing through Asia, U.S. Secretary of State Madeleine Albright repeated at every opportunity that the United States will not be cutting its forces in South Korea anytime soon.

The effects would also spread quickly beyond the Korean Peninsula. Since a Korean contingency has long been used to justify the U.S. presence in Japan, some claim that a Korean rapprochement would undermine the need for U.S. military bases here. But Akihisa Nagashima, a senior fellow at the U.S. Council of Foreign Relations who is studying the long-term U.S. presence in Asia, argued in an interview last month that the need for those bases remains compelling. Nagashima's thinking is simple: Regional stability requires a forward U.S. military presence in Asia. The status quo is unsustainable, however. The U.S.-Japan alliance must be modified to adapt to the new external environment if it is to provide peace and security in the 21st century.