The Lessons Learned for U.S. National Security Policy in the 20 Years Since 9/11

By Brian Katulis and Peter Juul

Getty/Drew Angerer: An American flag is left at the National September 11 Memorial, September 2017.

Americans will never forget the coordinated terrorist attacks on September 11, 2001, against the country’s financial center in New York, its global military headquarters at the Pentagon, and its civilian air transportation system. The images of New York police and firefighters rushing into the burning World Trade Center to rescue those trapped—and the memory of their sacrifices—will not fade from memory. America, its NATO allies, and the U.N. Security Council responded with swiftness and ingenuity to protect its citizens in the immediate aftermath and deployed measures to protect the their citizens, established new government agencies, and undertook numerous military operations overseas intended to eliminate threats and enhance stability.

The protective actions taken over 20 years have produced important gains in security at home—but these gains came with major human, financial, and strategic opportunity costs. The United States led international coalitions into three major wars in Afghanistan, Iraq, and against the Islamic State group in Syria and Iraq it also conducted military and intelligence operations in dozens of other countries. Admittedly, tallying gains against costs yields inconclusive results. What emerges clearly, however, is the consistency with which some of the biggest challenges emanate from unforced U.S. policy errors and unpredictable consequences of well-intended actions.

Today, the United States is more secure on the home front from foreign terrorist attacks yet faces increased domestic terrorist threats. America’s efforts to promote freedom and democratic governance in the world faltered. Freedom globally has stagnated and deteriorated since 2005, and the significant stresses on America’s own democratic system have risen dramatically in recent years.

The strategic ledger accounting for 20 years of effort remains decidedly mixed. There have been undeniable gains and signs of progress, but they came at great costs and too often spawned new challenges. However, there are lessons to be learned as the United States looks toward a national security strategy for the next two decades.

Gains and signs of progress

The United States is safer from foreign terrorist network threats A total of 2,977 people were killed in the 9/11 attacks, the largest single death toll from a foreign attack on America. Since then, 107 Americans have died in Salafi-jihadi terrorist incidents in the United States.

In the wake of 9/11, no additional major foreign terrorist attacks took place within the United States itself. This is the result of multiple lines of effort. The United States created new institutions, including the Department of Homeland Security, Directorate of National Intelligence, and National Counterterrorism Center. It substantially increased resources for intelligence and law enforcement agencies as well.

In addition, the United States implemented new security procedures to restore confidence in air travel. It developed new military and intelligence capabilities that helped thwart numerous plots and track down terrorist operatives and leaders, most notably Osama Bin Laden in 2011. The U.S. substantially enhanced its capacities to track and shut down terror finance networks, and it adapted its approaches to address terror threats in the cyber realm, staying in front of rapidly changing technologies. U.S. military and intelligence agencies created or strengthened counterterrorism partnerships across the globe, and these joint efforts helped the United States achieve more than it would have on its own.

These military, intelligence, and law enforcement efforts produced a key result: enhancing security at home. But some of these initiatives came with substantial financial, moral, and strategic opportunity costs.

America recognized the need to redefine national security and elevate nonmilitary tools of national power but fell short in making a fundamental shift toward a new approach

A few years into the initial U.S. policy response to the 9/11 attacks, the United States started to recognize the limits of a military-centric approach, with many political leaders, policymakers, and analysts calling for prioritizing diplomacy, economic tools, and political and ideological engagement. This growing recognition led to modest reforms, but the main structures and resources dedicated to so called “hard” security remained front and center. Efforts to integrate “smart power” as a central concept in U.S. national security failed to achieve the promised and desired results. Too often, the United States repeated past patterns of behavior in not using foreign assistance and other related tools effectively to achieve U.S. policy objectives.

A new generation came of age in more open societies in Iraq and Afghanistan

The wars in Afghanistan and Iraq removed authoritarian rulers from power and produced a qualified and tenuous sense of freedom in those countries that remained vulnerable to many security threats and challenges. The costs of these wars to these societies, America, and other coalition partners were substantial. But one gain that will endure are new generations of Afghans and Iraqis born after the start of these wars and who grew up in imperfect but more open societies. This new generation has shown a desire for positive change, as witnessed by the numerous waves of protest movements in Iraq in recent years and the continued participation in an open but imperfect electoral system. And while recent events in Afghanistan cast a dark shadow on these generational gains, Afghan youth—and women who had access to education and leadership roles—will likely make it more difficult for the Taliban to reimpose an old order.

Costs and sacrifices
The human costs and casualties of wars and conflicts have been staggering
It is difficult to capture the costs to human life in a wide range of efforts over two decades in dozens of countries. In post-9/11 military operations, the United States lost 7,074 troops killed in action and another 53,303 wounded. A further 1.8 million post-9/11 veterans have reported service-connected disabilities to the Department of Veterans Affairs. Furthermore, American allies and coalition partners lost 1,519 troops killed in action in Iraq, Afghanistan, and military counterterrorism operations elsewhere.

In addition, 18 American diplomats and aid workers were killed Middle East and South Asia since September 11, including seven in Iraq and three in Afghanistan. Twenty United Nations diplomats and workers were killed in attacks on UN facilities in Iraq and Afghanistan in 2003 and 2009. At least 10 diplomats from allied or coalition partner nations including Japan, Romania, the United Arab Emirates, Turkey, and Egypt were also killed in Iraq and Afghanistan over the past two decades.

Most estimates place the total number of deaths due to conflicts in Iraq, Afghanistan, and other countries part of the post-9/11 wars in the hundreds of thousands, including both civilians and combatants. However, it remains difficult to calculate precise numbers of those killed and wounded due to gaps and uncertainties in reporting.

Direct financial costs for U.S. taxpayers in the trillions
The total direct costs of the post-9/11 wars in terms of U.S. government spending are roughly $2 trillion over 20 years, including direct war costs and money spent on reconstruction, humanitarian aid, and efforts to build and support local security forces. This figure represents about 2.7 percent of the total U.S. federal government spending of more than $74 trillion during this 20-year period, a period when the total U.S. GDP was more than $335 trillion. These direct war and reconstruction costs amounted to less than 1 percent of overall GDP.

Large strategic opportunity costs

The 20 years of military operations and other efforts responding to the 9/11 attacks and other terrorist threats including the Islamic State group took time, resources, and attention away from other efforts needed to protect and strengthen the United States. In the international system, new transnational challenges such as pandemics and cybersecurity emerged, and state competitors such as China and Russia adopted more assertive stances in the global arena. As America focused on the battle against terrorist networks, the broader global landscape shifted.

While the base defense budget remains roughly similar as a share of GDP as it was before 9/11—2.78 percent of GDP in 2001 versus 2.86 percent of GDP in the Biden administration’s most recent budget request—the Department of Defense consistently invested in immediate priorities related to the wars in Iraq and Afghanistan rather than capabilities to counter longer-term challenges such as Russia or China. Secretary of Defense Robert Gates, for instance, stopped production of the F-22 Raptor stealth fighter in part because he saw it as useless in the wars in Iraq and Afghanistan.

A faltering struggle for freedom abroad begins to impact America at home
In the wake of the 9/11 attacks, many voices across America’s political and ideological spectrum backed a call to support freedom and democracy to counter the extremist ideas that fuel terrorist networks. The Bush administration initially framed its “Global War on Terror” in terms of a “Freedom Agenda,” and it justified some of its moves, including the 2003 Iraq War, within that framework. Yet missteps and unforced errors undermined America’s efforts to provide itself as an example of moral leadership in the world. This included high profile abuses, including the torture of detainees at prisons in war zones and around the world controversial drone strikes and broad intelligence collection programs that used new technologies to collect information in ways that raised questions about the checks and balances of America’s democratic political system.

Moreover, after decades of gains for freedom in the world beginning from the late 1970s, the tide started to turn in and around 2005. During the ensuing years—roughly over the past decade and a half—the world has witnessed stagnation and declines in political rights and civil liberties worldwide. In the Middle East and parts of South Asia, for example, despite enormous churn and shifts in power—including a series of protests starting in the 2011 Arab uprising and continuing until today—the fundamental picture for basic rights and freedoms remains bleak, with nearly all countries ranked as “Not Free” or “Partly Free” by Freedom House.

During the past five years inside of the United States, internal challenges to the country’s democratic system and mores emerged, with growing concerns about the stability and legitimacy of the election system and the broader system of government.

The battle of ideas is still not won and extremist ideologies and terrorist networks continue to take on new forms and spread

The extremist ideologies that were present 20 years ago have evolved, taken on different forms, and spread across the Middle East, Africa, and Asia.

Globally, the fight against Salafi-jihadi terrorism presents a mixed picture. U.S. special operations forces killed Al-Qaida leader Osama bin Laden in 2011. The United States has also had success in killing major terrorist leaders beyond bin Laden, including al-Qaida in Iraq’s Abu Musab al-Zarqawi al-Qaida in the Arabian Peninsula’s Anwar al-Awlaki and the Islamic State group’s Abu Bakr al-Baghdadi. America’s drone campaign against al-Qaida on the Afghanistan-Pakistan border appears to have proven successful in significantly degrading the core group’s capacity to carry out attacks. Likewise, the Islamic State group was deprived of its territorial control by a U.S.-led military campaign in Iraq and Syria.

Though groups such as the Islamic State group commanded the world’s attention in recent years, its Salafi-jihadi ideology has metastasized worldwide, with groups emerging in locations as seemingly unlikely as Mozambique. Terrorist groups motivated by this ideology have killed thousands in sub-Saharan Africa and the Asia-Pacific region over the past two decades, including the 2002 Bali bombing and 2008 Mumbai hotel siege that left hundreds dead.

The fall of Afghanistan to the Taliban following the U.S. military withdrawal likely represents a significant setback. The Taliban will likely provide safe harbor to al-Qaida and other Salafi-jihadi terrorist groups moving forward, and the U.S. military and intelligence community will face greater difficulty thwarting terrorist attacks with a hostile government in power in Kabul. As with the rise of the Islamic State group, it could give Salafi-jihadism an infusion of new energy.

Failed states continue to strain the international system
Chronic instability and a lack of effective governance in key parts of the Middle East, South Asia, and Africa leaves countries vulnerable to nonstate threats. This is not a necessary consequence of the past 20 years of U.S. action. Rather, it was a preexisting condition that did not improve. Initiatives aimed at helping other countries produce legitimate and effective governing authorities that were a part of the post-9/11 efforts in Afghanistan, Iraq, and other key countries failed to produce a major example of success. The weakest link in the post-9/11 efforts centered around the challenge of helping other societies develop governments that were effective and had broad legitimacy in the eyes of their own people. This complicated task involved a deep understanding of internal power dynamics and determining the best way to help other societies navigate major divisions—an understanding that the United States and other outside actors never fully acquired.