9/11, Post-Primacy, and
Defense Strategy Development

September 7, 2021   |   Professor Nathan Freier


September 2001 was Quadrennial Defense Review (QDR) and Defense Planning Guidance (DPG) season in the Pentagon. The QDR was the Bush-Rumsfeld DoD’s first crack at publicly reshaping the post–Cold War military.1 The DPG was the classified instrument by which the Rumsfeld team was to reprioritize military planning and resources to meet the QDR’s public-facing, transformational vision.2 Thousands of civilian and military staffers entered the Pentagon through the old Metro entrance on September 11, 2001, to analyze, contest, or operationalize every word, phrase, graph, and figure in the QDR and DPG.

On that day, none of the civilian or military staffers recognized the United States was already on a path to “post-primacy,” a strategic position within which the country would no longer dominate outcomes by default; rather, it would have to work “harder and smarter” to maintain its position and freedom of action in the face of mounting, purposeful opposition and resistance. On the morning of September 11, none of the Pentagon’s unsuspecting staffers knew that circumstances well beyond US control and US choices later that day and in the days, months, and years that followed would combine to impact profoundly and, in many cases, dangerously undermine America’s competitive global position. By day’s end, the World Trade Center and Pentagon had been attacked, and the United States was in the midst of a new, strategic decision-making context—the post-9/11 period; this moment was just a waypoint or transition to the much more challenging post-primacy period American strategists face today and for the foreseeable future.

Tuesday morning, September 11, 2001, was a beautiful, cloudless, early fall morning in Washington, DC. As the Pentagon workforce began settling into their desks, they were unwittingly experiencing the last few hours of unrivaled, US, post–Cold War primacy. For just a few more moments, they could enjoy the fiction of permanent and unassailable American strategic advantage. They could fight or defend their bureaucratic positions on the QDR and DPG believing, regardless of the outcomes inside the Pentagon, the United States would effectively dictate the terms of every consequential international security outcome in perpetuity outside the E-Ring.

They were wrong then, and we are paying for it now. Today, with the Afghanistan War’s difficult end and as defense and military leaders make a clean break from the post-9/11 era, they would be well advised to recognize their course and choices from this point forward must occur within and in response to the unique challenges of post-primacy. We are at peak vulnerability now as resistance to US influence and reach mounts. In post-primacy, the stakes are higher, the rivals more potent, the vectors and vulnerabilities ripe for hostile exploitation more plentiful, and the consequences of failure far more consequential than at any time since the end of the Cold War.


The shock of the 9/11 attacks was a “failure of imagination,” according to the blue-ribbon commission chartered to investigate it.3 Unfortunately, if imagination was in short supply in American defense strategy and strategic decision making pre-9/11, it remained so after and continues to lag today. Perhaps the most important lesson the US defense establishment should have learned from 9/11 and its aftermath was that American strategic decision making should not rely on international competition, conflict, and crisis emerging in a US-dominated environment and according to US preferences. Pre-9/11, the defense establishment did not heed warnings that world events will not always play by US rules. For example, pre-9/11 efforts like 1998–2001’s US Commission on National Security/21st Century—commonly referred to as “the Hart-Rudman Commission”—warned in the United States, “we will remain limited in our ability to impose our will, and we will be vulnerable to an increasing range of threats” through 2025.4 The commission got a great deal right. But even the commission did not predict the rapid onset of post-primacy.

Since World War II, US defense leaders have faced four distinct, strategic contexts within which they have had to make decisions: the Cold War, the post–Cold War era, the post-9/11 period, and, now, post-primacy. The post-9/11 period was a brief transition to today’s post-primacy, a warning of sorts of worse to come. While the United States exacted its pound of flesh over the course of 20 years, post-primacy was lurking and would ultimately come to be defined by its broad matrix of threat actors and their individual and collective hazard to strategic objectives, global position, and freedom of action. At Our Own Peril: DoD Risk Assessment in a Post-Primacy World, a 2017 US Army War College report on enterprise-level DoD risk, describes post-primacy according to four principal characteristics. These characteristics are:

  • hyperconnectivity and the weaponization of information and disaffection;
  • a rapidly fracturing, post–Cold War status quo;
  • proliferation, diversification, and atomization of effective, counter-US resistance;
  • resurgent but transformed great-power competition; and
  • the violent or disruptive dissolution of political cohesion and identity.5

This 2017 work benefited a great deal from lessons learned in the post-9/11 period. The United States’ power was more limited than strategic decisionmakers recognized. Rivals had seized on the post-9/11 period to identify and exploit US limitations to great effect. The barriers to entry into effective, counter-US resistance were also collapsing as the vectors by which states, groups, and individuals could resist became more numerous, and US vulnerability to their exploitation became more obvious. Among these vectors was the strategic influence space. The world was hyperconnected, and hyperconnectivity allowed for threat mobilization and popular manipulation through the strategic influence space at range and scale.6 At Our Own Peril also found all states—the United States and its allies, partners, and rivals—were overtly more self-interested. Thus, unilateralism was more universal, and alliances and partnerships were more transactional. In combination, these factors militated against uninterrupted US primacy.

These factors may not have been as apparent at the dawn of the twenty-first century, and US Army War College researchers had some ability to reflect clinically on where the United States had been since 9/11. Nonetheless, as the DoD set its future transformational course just before and after 9/11, these characteristic forces were either forming, emerging, or being discussed as future challenges.

The 9/11 attacks signaled the onset of post-primacy and its now-characteristic counter-US resistance. At first, the persistent challenges of terrorists and insurgents in the 2000s were the most obvious indications American defense leaders were entering uncharted international security waters. That would change dramatically over the next 20 years as the war on terrorism and post-9/11 wars in Iraq and Afghanistan dragged on, and even more contenders aimed at eroding US reach and influence. Perhaps most consequentially, rivals China and Russia availed themselves of American distraction to reignite transformed great-power competition.

The character and focus of US defense planning at the time of the 9/11 attacks and the subsequent US response to 9/11 indicated an exceedingly traditional perspective within US defense and national security circles. Post–Cold War primacy bred an air of American infallibility based on the same traditional perspective—recall the belief that competition, conflict, and crisis would unfold according to American preferences. After that, post-9/11 military demand around the world so obsessed US decision and strategy making it cloaked a troubling evolution in and response to the wider, counter-US threatscape that was emerging. Recall, for example, Secretary of Defense Robert Gates’ frustration with and response to Pentagon leadership he believed were focused too much on the future and not nearly enough on the fighting in Iraq and Afghanistan.7 Now, as the unique challenges of post-9/11 fade and those of post-primacy come out in sharp relief, Secretary Gates may have been exactly wrong.


In the post–Cold War decision-making context, US defense and military leadership failed to take heed of informed warnings like those of the Hart-Rudman Commission—for example, the now-infamous “Americans will likely die on American soil, possibly in large numbers.” This in spite of the fact that fundamental change in the international security order was already well underway and the United States’ place in that order was an open question. At the time, the officials charged with the defense and military security of the world’s sole, momentary “hyperpower” were either supremely (and mistakenly) confident in the permanence of unassailable US dominance, or they were somewhat incurious (or apprehensive) about what a more contested and less US-centric security order might portend for American interests in the future.8

By 9/11, the world was already changing faster than defense and military bureaucracies could possibly recognize or accommodate. Looking back, it is now clear the 2001 Bush-Rumsfeld QDR and DPG were artifacts of a hyperpower’s relatively short run. Add to this reality the challenges of inherent bias among defense and military decisionmakers—especially their preference to take on the threats most consistent with their cultural and institutional predispositions—and the DoD’s lack of foresight and unpreparedness for 9/11 and the post-9/11 onset of post-primacy were inevitable.

The 9/11 attacks and their aftermath provided US decisionmakers with ample warning that new threats, vulnerabilities, and levels of risk had arrived and would increase in potency and sophistication, regardless of countervailing US action. This period also provided an opportunity for US strategists to reassess the nation’s strategic position thoughtfully and recalibrate American strategy effectively and in ways more appropriate to an alien landscape where everything the United States wanted to accomplish would be increasingly and more effectively contested.

Unfortunately, the shock and horror of 9/11 disincentivized a more generalized reappreciation of the United States’ position in the world. In the end, primacy was cracking. Yet, primacy’s increasing fissures remained woefully underappreciated by US defense leadership for some time as they remained laser-focused on absolute and unattainable security against future acts of terrorism. Thus, in a defense and military context, American leadership held the door as post-primacy entered. But the game is not over.

Restating a conclusion of At Our Own Peril, post-primacy does not mean the United States is permanently defeated or persistently and irretrievably behind rivals that have effectively opted in on counter-US resistance. Post-primacy does mean, however, the United States is in disorienting and, to date, devitalizing territory. Past US defense and military leaders had grown used to doing what they wanted, how they wanted to, where they wanted, and when they wanted. Current leadership cannot behave this way. The United States will defend its interests for the foreseeable future in the context of many more exogenous (and endogenous) constraints than it faced through the post–Cold War and post-9/11 periods.

Since 9/11, the United States has been increasingly bested or outlasted by terrorists, insurgents, criminal enterprises, and great and middle powers precisely because these actors have opted not to adhere to America’s preferred rules for competition and conflict. Consistent with the 9/11 Commission’s conclusion, American challenges great and small since September 2001 are directly attributable to a continuing failure of imagination by senior US leadership. The root failure in this regard remains a deep-seated institutional inability within the DoD to recognize US vulnerability to hostile actors that seek and exploit advantage at American expense by persistently defying convention.

Rivals do this by both choice and/or necessity. However, it is no longer valid to minimize the hazard these actors pose by dismissing the trend as an indication of rival weakness. Instead, their methods and their ability to exploit them at US expense are the opposite of weakness and more an indication of their strategic acumen and guile. In the end, post-primacy is a period of peak U.S. vulnerability. It is clearly time the United States recognizes this vulnerability and thinks differently about how it might preserve military position and freedom of action against rivals that routinely exploit the nation’s affinity for convention.
Its September again in Washington, DC. Defense strategy development is underway. It is literally “QDR and DPG season” again 20 years on from 9/11. A great place to start the current planning season is recognizing the threat, vulnerability, opportunity, and risk inherent in an era of post-primacy. Adaptation to post-primacy is the United States’ most pressing defense priority. Maneuvering through this period successfully will require the DoD to regain the strategic initiative, neutralize counter-US resistance deliberately, shore up exposed American interests, and restore confidence in US military power. Achieving all these objectives will demand restored imagination.

  1. Office of the Secretary of Defense, Quadrennial Defense Review Report (Washington, DC: Office of the Secretary of Defense, September 30, 2001).
  2. “Defense Planning Guidance (DPG),” AcqNotes, updated July 11, 2021,
  3. National Commission on Terrorist Attacks upon the United States, The 9/11 Commission Report (Washington, DC: National Commission on Terrorist Attacks upon the United States, 2004).
  4. US Commission on National Security/21st Century, New World Coming: American Security in the 21st Century (Washington, DC: US Commission on National Security/21st Century, September 15, 1999).
  5. Nathan P. Freier et al., At Our Own Peril: DoD Risk Assessment in a Post-Primacy World (Carlisle, PA: Strategic Studies Institute, US Army War College, 2017),
  6. Nathan P. Freier, “Strategic Insights: Speed Kills—Enter an Age of Unbridled Hyperconnectivity,” US Army War College Press, June 9, 2017,
  7. Max Boot, “Why Is Robert Gates Angry?,” New Republic, February 25, 2014,
  8. International Herald Tribune Staff, “To Paris, U.S. Looks Like a ‘Hyperpower,’ ” New York Times, February 5, 1999,

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