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Research Questions

  1. What national security benefits does overseas presence provide?
  2. How does overseas presence affect total Department of Defense costs?
  3. What are the locations and numbers of forces needed overseas to execute the national military strategy?
  4. What changes are advisable in light of potential fiscal constraints, the changing strategic environment, the cost of maintaining overseas presence, and U.S. strategic interests?

Section 347 of the 2012 National Defense Authorization Act called on the Department of Defense to commission an independent assessment of the overseas basing presence of U.S. military forces. As the recipient of that commission, RAND's National Defense Research Institute conducted an independent assessment of the advisability of changes in the overseas basing presence of U.S. forces based on an evaluation of strategic benefits, risks, and costs. The report characterizes how overseas presence contributes to assurance of allies, deterrence, contingency responsiveness, and security cooperation, along with the risks involved with investing in facilities overseas. It breaks new ground in the understanding of the costs associated with overseas presence, including how permanent and rotational presence costs compare, and provides cost models for policymakers to weigh alternative posture options. To support this understanding of costs the report also lays out the conditions of U.S. installations and levels of host nation support.

The report concludes that there are certain minimum requirements necessary to carry out the current national security strategy, but it is prudent, based upon the net value produced, to maintain an overseas posture that goes beyond these minimums. Additionally, it combines benefit, cost, and risk considerations to distill a number of strategic judgments that have implications for the advisability of considering identified posture changes.

Key Findings

Overseas presence contributes to contingency responsiveness, deterrence, assurance, and security cooperation.

In many cases — but not all — overseas presence enhances contingency responsiveness.

  • In-place forces are critical for the initial stage of major contingencies.
  • The global en route infrastructure enables reinforcement of in-place forces and broad responsiveness.
  • Access to bases from which direct air support can be provided is important.
  • Global naval presence contributes to response flexibility.
  • Overseas ground forces may not provide an advantage for regional responsiveness when not proximate to the area of conflict.

Overseas forces targeted to specific threats provide deterrence and regional assurance.

  • In-place forces signal the ability to thwart quick victories and assure allies of U.S. commitments.
  • Regional air and missile defenses protect and assure allies and partners.

Overseas presence enhances security cooperation, which builds U.S. capabilities to work with partners and helps develop their capabilities.

  • The marginal cost of security cooperation activity for forces based overseas is low, resulting in higher activity.
  • The greatest benefits accrue from working with advanced partners.

Basing has fixed and variable cost elements, with variable costs per person (and overall costs) higher overseas, even when taking host-nation support into account.

  • Consolidation by closing a base (anywhere) cuts the fixed cost.
  • Realigning forces from overseas to the U.S. reduces costs due to the variable cost difference.

The costs of rotational presence can be more or less than overseas stationing, depending on rotation frequencies, lengths, unit types, and locations.

Some posture changes could be advisable, depending on judgments about national security priorities and the relationships between posture and strategic benefits.

  • Further reductions in Europe would reduce costs, but at some penalty in terms of security cooperation and assurance of allies.
  • The emerging threat from long-range precision-guided weapons needs to be part of the calculus when adjusting posture in the Asia-Pacific region in the pursuit of deterrence and assurance goals.
  • In Asia, another key consideration is the value of having ground forces stationed in the region versus in the United States for flexible contingency response, assurance, and security cooperation with partners across the region.
  • In the Persian Gulf, policymakers must weigh the deterrent benefits of presence against the costs and the risks driven by host nations' political sensitivities to U.S. presence.

The research described in this report was prepared for the Office of the Secretary of Defense (OSD). The research was conducted within the RAND National Defense Research Institute, a federally funded research and development center sponsored by OSD, the Joint Staff, the Unified Combatant Commands, the Navy, the Marine Corps, the defense agencies, and the defense Intelligence Community.

This report is part of the RAND research report series. RAND reports present research findings and objective analysis that address the challenges facing the public and private sectors. All RAND reports undergo rigorous peer review to ensure high standards for research quality and objectivity.

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