There are other, deeper problems . . . . Unresolved structural difficulties in the rok economy (including, but not limited to, the rapid graying of the rok population, the to-date tentative progress in desperately-needed corporate and financial reforms, the fragility of the country's service industries, and the country's continuing difficulties in establishing a domestic scientific-research infrastructure) promise to generate-and exacerbate-economic frictions in the U.S.- rok relationship. All else equal, and no matter which party wins in December, such frictions will prompt voters to scrutinize the U.S. military alliance more carefully than ever, and to be less deferential in raising questions about the nature of the alliance's burdens.

An American troop withdrawal from Korea -or its downgrading into a peacekeeping force-would generate far-reaching reverberations (though some U.S. analysts favor such a course of events). One such reverberation would concern the future of U.S. forward basing in Japan. For Japan to be the only East Asian state hosting U.S. troops, this on top of the continuing controversy in Japanese domestic politics with regard to Okinawa, might be hard to sustain for long in Japanese politics. Thus, an American military pullout from South Korea, far from leading to a bolstering of U.S. forces elsewhere in East Asia, might trigger a major diminution of American influence in the Pacific.

The worst of all outcomes would be a politically rancorous American withdrawal from Korea at a time when a highly armed North Korean state fronting an effective charm offensive saw opportunities to further its old ambition-the re-unification of the peninsula under its aegis. Those particulars could all too easily lay the stage for a potentially explosive and devastating conflict in Korea, with spillover potential to other major powers.

But even presuming genuine rapprochement between North and South and some measure of stability in Korea, an American withdrawal from Korea would still create a security vacuum and invite a latter-day version of the Great Game of realpolitik the Pacific powers played so roughly in the region a century ago. A U.S. military withdrawal from Korea might be welcomed in Moscow or Beijing, but, in truth, both are ambivalent about the American military presence in Korea. In public they support U.S. withdrawal, but privately they recognize that Northeast Asia would be a more risky and less stable neighborhood-and a region less disposed to economic growth-without the U.S. military presence. Although any losses-in terms of diminished economic potential and reduced national security-would be distributed unevenly in the region, all the Pacific powers and South Korea would lose from an end to the U.S.-rok military alliance and the U.S.-dominated security order in East Asia. Of all the political actors in East Asia, only the dprk-the region's lone radical revisionist state-could reasonably expect any benefits.

Absent a convincing rationale, the Mutual Defense Treaty-and the forward deployment of U.S. forces in Korea it provides for-cannot count on the continued support from both the South Korean and American publics that is necessary to sustain it. Since it is manifestly in the interests of Seoul and Washington to keep the U.S.-rok military alliance in good repair, it is incumbent upon American and South Korean policymakers to elucidate that rationale.

The original rationale-premised on the risk of hostile external maneuvers against South Korea-may not yet be so passé as some think. If and when the day arrives that the North-South struggle is no more, however, a compelling rationale for a continuing rok-U.S. alliance can still be made, based upon deterring instability in an economically important, too well-armed, and not-yet-solidly-liberal international expanse. On both sides of the Pacific, national audiences wait to be persuaded of that rationale. Statesmen who understand the value of the relationship would be well advised to devote a little more effort to the task.

Nicholas Eberstadt holds the Wendt Chair in Political Economy at the American Enterprise Institute for Public Policy Research, Washington dc. This essay draws upon and updates an earlier work in Strategic Asia 2001-02: Power and Purpose, Richard J. Ellings and Aaron L. Friedbuerg eds., (2001).