Twenty-five years ago today, the United States was attacked in a way that changed America and the world. For many Americans today, particularly younger generations, September 11, 2001, is history. For me, it is personal. I was in my office in the Pentagon that morning, only two corridors away from where American Airlines Flight 77 struck the building. I remember the impact, the smoke, the confusion, and the realization that our nation was under attack.
A few days later, the Chief of Staff of the Air Force, Gen. John Jumper, called me to his office and asked me to return to the Middle East to help plan America’s air response to the attacks as commander of the Combined Air Operations Center. That sequence—from an attack on our homeland to planning and executing a global military response in a matter of days—demonstrated something fundamental about American airpower: speed, reach, flexibility, and the ability to create strategic options on very short notice.
The Strategic Lesson of 9/11
But a quarter century of hindsight provides another, equally important lesson. The United States became extraordinarily effective at finding, tracking, and eliminating terrorist threats around the world. The men and women who fought the Global War on Terror displayed extraordinary courage, ingenuity, and professionalism. Their efforts disrupted terrorist organizations, eliminated their leaders, prevented attacks, protected our homeland, and provided our political leaders with options across the globe.
Those missions were necessary. But we also learned that extraordinary tactical performance—and even overwhelming military success—does not automatically translate into strategic success.
Military effectiveness is necessary for strategic success, but it is not sufficient. Military force can create opportunities, impose costs, destroy enemy capabilities, and establish conditions for political objectives to be achieved. It cannot compensate indefinitely for unclear objectives, shifting end states, or policies disconnected from military realities. That is one of the most important lessons America should take from the 25 years since 9/11. There is another.
The Threat Has Changed
We cannot allow the threats that dominated the last quarter century to define the military we need for the next one. The terrorist organizations that attacked the United States and threatened Americans around the world were dangerous and had to be defeated. But the scale of the challenge they presented pales in comparison with the threats confronting the United States today.
China is executing the most consequential military buildup of any nation in decades and has developed forces explicitly designed to counter American military advantages. Russia possesses the world’s largest nuclear arsenal and has demonstrated its willingness to use military force to change international borders. North Korea possesses nuclear weapons and ballistic missiles capable of reaching the United States. Iran has spent decades developing missiles, drones, proxy forces, and other means to attack American interests and our allies.
Increasingly, these nations are cooperating with one another. They are not a NATO-like alliance, nor are their interests identical. But they share a desire to constrain American power, weaken U.S. influence, and undermine the international system from which the United States and its allies have benefited. The U.S. intelligence community has warned that their selective cooperation is already strengthening the threats each poses individually.
This is a fundamentally different security environment from the one America faced after the Soviet Union collapsed. Unfortunately, while our adversaries were building military capacity, the United States spent decades reducing and consuming ours.
America Spent Its Peace Dividend
Following the Cold War, successive administrations of both parties harvested the so-called peace dividend. Force structure declined. Aircraft inventories shrank. Ships aged. Munitions stocks proved inadequate for prolonged high-intensity warfare. Readiness suffered. The industrial base contracted. We repeatedly accepted near-term risk on the assumption that technological superiority could compensate for diminishing capacity.
Technology matters enormously. But there comes a point when capacity matters too—and we have let that attribute atrophy far too low. The U.S. Air Force provides a particularly stark example. It is now the oldest and smallest in its history, while demands are growing for its capabilities—in sufficient quantities—across Europe, the Middle East, the Indo-Pacific, and the homeland simultaneously.
National Defense Is a National Priority
This is not simply a Department of War problem. It is a national priority problem. Consider where we are today. CBO projects roughly $1.0 trillion in net interest outlays versus $918 billion in total defense outlays in FY2026. Defense discretionary spending amounts to only about 2.8 percent of GDP—the lowest level recorded since 1962. CBO projects mandatory federal spending at roughly $4.5 trillion this year; add more than $1 trillion in interest payments, and those two categories consume roughly three-quarters of all federal spending.
Think about what that means. The United States now spends more servicing yesterday’s debt than providing for today’s national defense. That is not sustainable for a nation that intends to remain secure, prosperous, and free.
This does not mean abandoning Social Security, Medicare, or commitments Americans have planned their lives around. Nor should the defense establishment be exempt from demands for efficiency, accountability, and reform. Every federal dollar should be spent wisely. But arithmetic is arithmetic. We cannot indefinitely allow mandatory spending and interest costs to crowd out the fundamental constitutional responsibility to provide for the common defense.
National security is not simply another federal program competing for a share of the budget. It is the prerequisite that makes every other national priority possible. The consequences of inadequate deterrence would dwarf the fiscal adjustments necessary to restore it. Americans understandably worry about the cost of rebuilding our military. They should also consider the cost of failing to do so.
If deterrence fails in the Indo-Pacific, Europe, the Middle East, or on the Korean Peninsula—or worse, in several theaters simultaneously—the economic consequences would be measured not simply in billions of additional defense dollars, but potentially in trillions of dollars of lost commerce, disrupted supply chains, destroyed infrastructure, shattered financial markets, and human suffering.
Deterrence Is Far Cheaper Than War
Peace is far less expensive than war. But peace does not result from good intentions. It is sustained by credible deterrence. And credible deterrence depends upon adversaries believing two things: that the United States possesses both the capability and the will to defeat aggression.
Twenty-five years ago, our nation discovered in a single morning what can happen when an adversary believes it can strike the United States and achieve its objectives. We responded decisively. Thousands of Americans subsequently served, fought, sacrificed, and died defending this nation. We owe it to them to remember not just what happened on September 11, but what it teaches us. The lesson is not that America should remain perpetually at war. The lesson is that we must possess the strength necessary to prevent wars whenever possible—and to win them decisively when prevention fails.
Today, the challenge is much greater than terrorism. We face powerful states armed with nuclear weapons, long-range missiles, advanced aircraft, submarines, cyber capabilities, space systems, and rapidly expanding conventional forces. Some possess the ability not simply to hurt Americans, but to threaten the fundamental security and prosperity of the United States and its allies. Yet we are confronting this deteriorating security environment with a military that has been allowed to shrink for more than three decades and a fiscal trajectory that increasingly constrains our ability to rebuild it. That must change.
September 11 should remind us that threats ignored do not disappear. Vulnerabilities left unaddressed are eventually discovered. And deterrence is infinitely preferable to responding after Americans have already been attacked. The best tribute we can pay to those we lost on 9/11—and to all those who served and sacrificed in the 25 years that followed—is not simply remembrance. It is to learn.
America must once again treat national defense as a first-order national responsibility, rebuild the military capacity required to deter today’s threats, restore the industrial base necessary to sustain it, and align our fiscal priorities with the world as it actually exists—not the world we might wish existed.
Because ultimately, providing for our collective security is not a choice between defense and our national welfare. Without security, our national welfare—and our way of life—are at risk.
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