The 2009-2010 exercise is the fourth Quadrennial Defense Review carried out under that name and the sixth comprehensive reexamination of U.S. defense policy since the end of the Cold War. Changing Perspectives on the Global Security Environment

Looking at the cumulative results of post-Cold War defense reviews, beginning with the 1990 Base Force analysis and the 1993 Bottom-Up Review and culminating in the 2010 QDR, the net effect has been a substantial change in the conceptual underpinnings of U.S. defense strategy. The four QDRs, in 1997, 2001, 2006, and 2010, can perhaps best be seen as snapshots of an ongoing evolution of strategic thinking away from planning for smaller versions of Cold War-era conventional conflicts, on the model of the 1991 Persian Gulf War, and toward planning to cope with a much more diverse array of challenges and responsibilities. By the time of the 2006 and 2010 QDRs, the basic strategic assumptions guiding military planning had shifted dramatically. One premise is that no future adversary is likely to confront U.S. conventional, Cold War-era military capabilities directly. Instead, any foe, ranging from violent, radical non-state terrorist groups to a technologically advanced near-peer competitor, will try to exploit weaknesses in U.S. defenses through asymmetric means. So the notion of a spectrum of conflict, ranging from unsophisticated insurgents or terrorists at the low end to sophisticated national armies at the high end, is becoming blurred. The 2010 QDR concludes that changes in the global security environment require some adjustments in the balance of investments among elements of the U.S. military force posture. It argues for an emphasis, first of all, on prevailing in current conflicts in Iraq and Afghanistan and against Al Qaeda elsewhere. For future planning, it calls for new initiatives in a number of joint mission areas, including homeland defense, countering weapons of mass destruction, the ability to project power into key regions of the globe in the face of challenges to U.S. access, building the capacity of partner nations to defeat terrorism, and means of ensuring access to cyberspace. Outline of this Report

This CRS report (1) cites the legislative mandate for the QDR and reviews legislative requirements for a number of related reports; (2) outlines the results of the 2010 QDR; (3) identifies what is new in the 2010 review and discusses how thinking on key matters has evolved; (4) reviews some common criticisms of the 2010 QDR and of the QDR process; (5) discusses whether the quite radical changes in the nature of conflict that the 2006 and 2010 QDRs describe have been reflected in sufficiently far-reaching changes in defense plans and programs, and (6) concludes with a discussion of matters that future QDRs—or a more extensive interagency study—might address more fully as a means of putting defense planning into the context of a broader perspective on U.S. national security. It is likely to be a major new investment in future years. These include many measures to cope with anti-access strategies, measures to counter anti-satellite systems, and cyberwarfare initiatives. Should the QDR Address Broader Security Issues? The principal policy matters that directly shape defense planning include
When and under what conditions to use military force; Effects of global financial trends on long-term security planning; Effects of long-term domestic economic and budget trends on defense planning; The effect of growing costs of personnel, operations, and acquisition on long-term defense plans; The evolution of Cold War-era alliances in the post-Cold War era; Global cooperation and global rules of behavior on proliferation, terrorism, human rights, and democratization; The integration of defense and non-defense responsibilities in national security policy. (f) Independent Panel Assessment.
On February 1, 2010, the Defense Department released a report on the 2010 Quadrennial Defense Review (QDR), a legislatively mandated assessment of defense strategy and priorities. The review is the sixth full scale assessment of U.S. defense policy since the end of the Cold War, beginning with the 1990 Base Force analysis and the 1993 Bottom-Up Review and continuing with QDRs completed in 1997, 2001, 2006, and 2010. These official reviews have been supplemented by assessments of independently chartered panels.
The four QDRs reflect an ongoing evolution of strategic thinking away from planning for smaller versions of Cold War-era conventional conflicts, on the model of the 1991 Persian Gulf War, and toward planning to cope with a much more diverse array of challenges. By the time of the 2006 and 2010 QDRs, the basic strategic assumptions guiding military planning had shifted dramatically. One premise is that no future adversary is likely to confront U.S. conventional, Cold War-era military capabilities directly. Instead, any foe, ranging from violent, radical non-state terrorist groups to a technologically advanced near-peer competitor, will try to exploit weaknesses in U.S. defenses through asymmetric means. A related premise is that the notion of a spectrum of conflict, ranging from unsophisticated insurgents or terrorists at the low end to sophisticated national armies at the high end, is becoming blurred, with "low-end" terrorist groups using advanced technologies and near-peer competitors likely to use indirect means of attack.
The 2010 QDR concludes that changes in the global security environment require some adjustments in the balance of investments among elements of the U.S. military force posture. It argues for an emphasis, first of all, on prevailing in current conflicts in Iraq and Afghanistan and against Al Qaeda elsewhere. It revises force planning to put diverse, overlapping scenarios, including long-duration stability operations and defense of the homeland, on a par with major regional conflicts in assessing the size and composition of the force. And, it calls for new investments in critical joint missions, including countering "anti-access strategies" aimed at defeating U.S. power projection forces; building the capacity of partner states; and ensuring access to cyberspace. The 2010 report also proposes measures to reform institutional procedures that it sometimes describes as "relics of the Cold War," including acquisition, security assistance, and export control processes.
Critiques of the current and earlier QDRs raise a number of issues: Is the review overly constrained by budget limitations? Does it make sufficiently disciplined choices among the many priorities it cites? Does the focus on current conflicts come too much at the expense of preparations for future conflicts? Does the review realistically assess threats from Russia and China? A fundamental issue is whether the quite radical reassessment of global security challenges in recent QDRs has been matched by sufficiently far-reaching changes in the composition of the force.
A question for future QDRs may be whether the reviews should be tasked to address broader security policy issues as a means of assessing defense plans in a more complete context. Potential policy issues to address include when to use military force, the effects of global financial trends on U.S. defense plans, the effects of domestic economic and budget trends on defense resources, the evolution of alliances to reflect post-Cold War era challenges, the prospects for more cooperative global security rules and institutions to enhance security, and the integration of U.S. defense planning with broader, interagency policies to address global trends.