U.S. Military Strategy and Force Posture for the 21st Century

It is not certain that these revolutions will inevitably result in international turmoil, but neither is it clear that they will not. In light of this uncertainty, the United States should not commit to a military strategy that assumes a stable international system for the next two decades. Needed is a new concept with a broader set of objectives than that of the Regional Strategy. Such a concept ties U.S. military strategy both to the international security system and to the domestic agenda. Its core objectives are to deter regional threats, to discourage attempts at global hegemony, and to prevent multipolar rivalries. Concurrently, the concept calls for the United States to assist in developing a cooperative and healthy world economy. This strategy works to produce a safe, stable world that, in turn, protects U.S. interests, fosters a prosperous U.S. economy, and results in an adequate but affordable defense budget.

The new strategy resembles the Regional Strategy in that it accepts the need to be able to deal with two roughly concurrent MRCs and a force the approximate size of the Base Force. But it proposes different strategic foundations. Casting aside the focus on deterrence and containment, it seeks a new set of regional security mechanisms that balance military power, promote a sense of community, and discourage aggression and competitive multipolar rivalries. Nuclear forces will decline in importance as conventional forces assume larger roles in U.S. military strategy. But these forces will have to be capable of a wide range of missions, both combat and noncombat.

Different Strategies for Different Worlds

The five revolutions under way could play out in very different ways, ranging from far better than today to far worse in terms of global stability. Thus, defense planners need to think of the different strategies that might be pursued under the alternative circumstances. The different worlds will impose a range of military requirements, and it is important to understand how choices made today will affect the United States' ability to respond to the future. The figure depicts the range of future worlds and the level of military requirements as a percentage of today's Base Force.

The most optimistic case, a world of global harmony, would offer tranquil relations among major powers and little risk of regional conflicts. The U.S. military strategy would aim at preserving harmony and dealing with the limited conflicts that remain. In this climate, concurrent MRCs would be unlikely and the U.S. force posture could be 20-35 percent smaller than the Base Force. On the other end of the spectrum, an unstable multipolar world would include tense relations with Russia and China and a collapse of today's system of alliances. Thus, NATO has disintegrated and U.S. relations with a nuclear-armed Japan have degenerated to strategic confrontation. The U.S. military strategy would focus on maintaining balance among Russia, China, the European Union, and Japan. Force requirements would include the full range of nuclear deterrents and a large expeditionary force capable of waging major wars in Europe and Asia.

Mission-Based Capability Analysis

Determining the force levels for this range of contingencies is difficult. The traditional approach of threat-based contingency analysis has lost its usefulness because postulated threats lack credibility, and the planning factors that underpin it have not kept pace with the changes in military technology and doctrine. Recognition of the shortcomings of contingency analysis has led some to propose a resource-based capability analysis, which focuses on the desired capabilities of a force rather than a specific threat. Although useful in many regards, this methodology also falls short of answering questions about total force size because it fails to define requirements clearly.

Instead, the author argues for a mission-based capability analysis that bridges the gap between the other two methodologies. It measures adequacy in terms of capabilities, not domination of specific threats. And it looks to capabilities in terms of outputs, not resource inputs. The methodology assumes that the nature of future wars is uncertain and therefore focuses on the kinds of strategic wartime missions U.S. forces should be capable of performing. The strategic premise of this methodology is that the United States can defend its interests if it can deploy sufficient forces to two MRCs and retain a pool of uncommitted forces for other purposes. The methodology postulates that U.S. forces must be simultaneously capable of five different strategic missions:

  • Rapid deployment of a joint U.S. field army capable of overwhelming force in one MRC
  • Prompt deployment of a second force, largely composed of active units, capable of defensive operations in a second MRC
  • Maintenance of a small strategic reserve composed of active and reserve units
  • Maintenance of a rotation base of reserve forces
  • Maintenance of reinforcements, provided by the reserves, that could enlarge either or both MRCs should requirements expand.

These missions impose a range of military needs. If requirements are high across all five missions, the Base Force would not satisfy them but would suffice in most situations. Because the Base Force contains a margin of safety, it could sustain reductions in the range of 10-15 percent and still be adequate. Deeper reductions would compel decisions about priorities among the multiple missions.

RAND research briefs summarize research that has been more fully documented elsewhere. This research brief describes work done in the National Defense Research Institute and documented in MR-328-JS, U.S. Military Strategy and Force Posture for the 21st Century: Capabilities and Requirements, by Richard L. Kugler, 228 pp.. You may also order a copy by clicking on the document number. RAND is a nonprofit institution that helps improve public policy through research and analysis. RAND's publications do not necessarily reflect the opinions or policies of its research sponsors.