U.S. Forces in Korea

President Trump appears to have restrained his impulse to withdraw U.S. forces from South Korea at this week’s Summit. That was wise. As negotiations proceed, a unilateral drawdown of American military personnel should continue to be off the table. It would degrade our negotiating position on the peninsula, harm our ability to protect Americans and secure our economy, and reduce our advantages against potential military threats from China and Russia. Most ironically, withdrawing U.S. forces would likely leave American taxpayers with a significant bill. Reducing tensions on the Korean peninsula is a goal all parties can get behind, but there are smarter and cheaper ways to do it than withdrawing U.S. forces.

The United States will want its military presence in South Korea in almost any set of foreseeable circumstances. As negotiations proceed, it should remain to check North Korean nuclear, chemical, biological, and conventional capabilities. In the event of a verifiable agreement, it will likely take a decade to dismantle the most worrisome of these capabilities, time in which the current or next North Korean regime could present new or renewed threats. Even if full and lasting peace breaks out on the peninsula, South Korea could serve as a strategic location for U.S. forces, looking west toward South Asia, north toward Russia, or east toward China. The need for a sizable joint force in the Pacific beyond Korean contingencies may seem hard to imagine, but history cautions humility in the face of America’s repeated failures of imagination. Moreover, a credible force in South Korea supports President Trump’s own “peace through strength” rhetoric: if we hope never to employ our forces in the Pacific, we should begin by ensuring we have a capable force posture that deters would-be adversaries.

One need not subscribe to a domino theory of state behavior to appreciate the strategic risks of a precipitous unilateral disengagement from South Korea. Absent unified U.S.-Japan-South Korea support, such a move could be devastating, shifting the Pacific balance of power, including economic sway, away from the United States. Such an indisputable sign of U.S. disengagement from long-standing security guarantees could speed similar dynamics in Europe.

There are operational challenges to positioning U.S. forces close to enemy capability. Yet it would be unwise to respond to force vulnerability concerns with a reflexive garrisoning of U.S. capability in the continental United States. Depth matters, but so does speed, particularly given that the most likely challenges we would seek to deter—and win if deterrence fails—might begin with a small confrontation that escalates quickly. As in Europe during the Cold War (and today), U.S. and allied forces in Asia need to design a mix of forward and over-the-horizon forces appropriate to the broad range of potential crises that might unfold. This will likely place a premium on our ability to disperse in-theater forces quickly, protect emplaced and maneuvering forces, and have an approach to global force management that provides for the deployment of ready forces from other regions, including the United States.

Cost will almost always be a consideration in determining where to posture military forces, but it does not always point our soldiers, sailors, airmen, and marines toward home. Personnel savings would materialize should the United States reduce the size of its overall force, but if it seeks to reposition them, the cost calculus is more complicated. Deciding to sacrifice lethality by not readying or employing our forces would also reduce costs. However, if the United States wants to retain roughly the military end-strength and force structure it has today, but position much less of it overseas, it would need substantial new investments in domestic training ranges, housing, and other facilities. A force that is never or seldom used could be most cheaply kept wherever land costs are low and land is plentiful, such as remote locations in the United States. Upfront costs will be substantial, with a lengthy payback period. Assets and forces dependent on coastal access would be particularly challenged to expand current footprints inexpensively. The United States would also forego the substantial direct and indirect host-nation support that South Korea provides. Instead, U.S. taxpayers would pick up the full bill. If, to our surprise, U.S. forces are needed overseas routinely, operating costs would skyrocket.

The United States can and should adapt its presence on the Korean peninsula, taking account of changing geopolitical, military-technical, and feasibility considerations. But the capability of this forward force should remain significant. In pursuit of a full and lasting peace on the peninsula, confidence-building measures to reduce U.S.-ROK and North Korean capabilities are possible. However, they should be mutual and aimed at reducing the full arsenal of North Korean capability: chemical, biological, and conventional, as well as nuclear. For example, the U.S.-ROK alliance and the North Koreans might consider standing down military capability along the demilitarized zone (DMZ). North Korea would need to stand down at a greater distance than forces in the South, given the relative proximity of Seoul and distance of Pyongyang to the DMZ, but past North Korean negotiating teams seem to have acknowledged this likelihood. Mutual “freeze for freeze” approaches on exercises could likewise be considered, but they should never deny South Korea and the United States from preparing combined forces for non-peninsula contingencies and from appropriate self-defense measures. President Trump’s agreement to suspend the upcoming U.S.-ROK combined exercise does not appear to meet this threshold for protecting U.S. lethality, and should not be advanced absent substantial North Korean concessions.

Kathleen H. Hicks is director of the International Security Program, Henry A. Kissinger Chair, and senior vice president at the Center for Strategic and International Studies in Washington, D.C. She served in the Obama administration as principal deputy undersecretary of defense for policy and deputy undersecretary for strategy, plans, and forces.

Commentary is produced by the Center for Strategic and International Studies (CSIS), a private, tax-exempt institution focusing on international public policy issues. Its research is nonpartisan and nonproprietary. CSIS does not take specific policy positions. Accordingly, all views, positions, and conclusions expressed in this publication should be understood to be solely those of the author(s).

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Kathleen H. Hicks