U.S. Forces Face Strategic Trade-Offs

By Lynn E. Davis

Lynn Davis, a senior political scientist, is director of RAND's Washington office.

Since World War II, the United States has relied on a network of global military bases and forces to provide forward, collective defense against the Soviet Union, to counter the proliferation of weapons of mass destruction, and to fight terrorism. Today, the international environment has changed, with China asserting itself across East Asia, Iran pursuing an ambitious nuclear program, and al Qaeda affiliates still posing threats to Western interests. Domestically, too, the environment is changing, as the United States confronts serious economic uncertainties and growing pressures to reduce defense spending.

It is not surprising, therefore, that a debate is under way as to the future role of America in the world, specifically regarding the size and characteristics of the U.S. overseas military presence. Whereas the Obama administration has called for a global presence that emphasizes the Asia-Pacific region and the Middle East while maintaining defense commitments to Europe, other voices have called for bringing most U.S. military forces home.

For the U.S. military, the first challenge is to decide whether U.S. allies in Europe and Northeast Asia are willing to assume primary responsibility for their own security; if so, this would allow the United States to reduce its overseas presence. If relying more on the allies seems too risky, one option would be to rely primarily on U.S.-based forces to respond to global crises. If that option also seems untenable, then the United States will have to choose whether to focus its overseas presence more on Asia or on the Middle East. America cannot do it all. But if U.S. defense leaders can agree on their highest global priorities, then the tough budgetary decisions will be easier to make, and the highest priorities will more likely be served.

Assessing U.S. Options

It is useful to review U.S. global security interests. Recent U.S. strategy and defense documents have identified seven discrete and enduring interests:

• protecting U.S. allies and partners from state adversaries
• promoting U.S. influence in key regions
• dissuading military competition and arms races
• protecting Americans from terrorist attacks
• restricting the flow of illegal trade and the proliferation of dangerous materials
• ensuring the flow of commerce and key resources
• responding to humanitarian emergencies and regional conflicts.

A RAND team focused its attention on the first three interests above because they involve major threats to the United States and will likely be the main drivers in determining the future U.S. overseas presence. Because U.S. officials differ on what type of overseas presence is needed to serve these interests, the team compared five global postures in terms of their ability to do so.

The five alternative postures were, in brief, a shared U.S. and allied global presence, a shift to a U.S.-based long-range posture, an expanded U.S. global forward presence, an expanded U.S. forward presence only in Asia, and an expanded U.S. forward presence only in the Middle East. What emerged from comparing these postures and their likely consequences are the critical choices that U.S. officials need to make and that the U.S. public needs to debate.

Making Strategic Choices

The first strategic choice for the United States is to decide whether its overseas military presence can be reduced and diversified because its allies in Europe and Northeast Asia have the ability, economically and militarily, to assume primary responsibility for their own security. Such a choice could involve the United States reducing bases and combat forces in Britain, Germany, Japan, and South Korea. The remaining permanent U.S. overseas presence would provide the bases and forces for immediate responses to future threats and to reassure U.S. allies and partners. The United States would then have the flexibility to expand its presence across Southeast and Southwest Asia if threats in those areas were to increase or if partners were to request assistance.

AP IMAGES/THE NIAGARA GAZETTE, JAMES NEISS

Members of the 914th and 107th Airlift Wings listen to U.S. Secretary of Defense Leon Panetta at the Niagara Falls Air Reserve Station in Niagara Falls, New York, on August 9, 2012. He said the Pentagon is committed to protecting the western New York air base, which has been the target of potential cutbacks.

If relying more on U.S. allies seems risky, given their reliance on nonmilitary responses to potential military threats and their political and economic constraints, the United States would face other strategic choices. One is whether it is time for the United States to rely primarily on U.S.-based forces to respond to global crises and conflicts, keeping only a small global forward presence to reassure allies and partners. Such a choice would be based on the perspective that deterring and responding to China, North Korea, and Iran will depend not on a permanent U.S. overseas presence but rather on the ability of U.S. military forces at home to surge into those regions in the event of crises or conflicts. Relocating U.S. military forces to the United States would have the advantage of reducing their vulnerability to expanding missile threats.

Choosing to reduce the U.S. overseas military presence would not make sense, however, if leaders decide that such a presence plays an important role in deterring and responding to one or more of the threats from China, North Korea, or Iran and in reassuring U.S. allies and partners. The strategic choice that then arises is whether the United States should maintain its global posture essentially as today and prepare to increase its overseas presence in Southeast and Southwest Asia if threats expand there. Retaining existing bases would have the advantage of reducing the risks associated with not being able to return to those bases after giving them up.

Such a robust global posture, though, could become too expensive or politically problematic. Therefore, the final strategic choice would be whether the United States should focus its overseas presence more on Asia (because of China's expanding military activities) or more on the Middle East (because of threats to stability and the flow of oil from a potentially nuclear-armed Iran).

Focusing on Asia would mean keeping U.S. bases and military forces in Japan and South Korea, then expanding deployments and exercises to the extent that they become politically feasible with countries in Southeast Asia. Focusing on the Middle East would mean keeping U.S. bases in the Gulf Cooperation Council states and in Africa to quickly blunt any attacks on U.S. partners in the region while relying on surging military forces from the United States for contingencies in Asia. In either case, the choice would require the reorientation of U.S. military forces in Europe to assist any surge of forces from the United States in response to crises and conflicts in whichever region (the Middle East or Asia) where the U.S. presence would be reduced.

Those debating the future U.S. global posture need to make explicit their perspectives on what role U.S. military forces should play overseas and then decide from the menu of strategic choices outlined above. While there are no right or wrong choices, focusing first on U.S. global security interests makes it more likely that the selected overseas presence will best serve the highest interests and not be based on unrelated considerations, such as the political pressures of allies and congressional leaders.