“No day shall erase you from the memory of time.”

— Virgil, inscribed at the National September 11 Memorial & Museum

Twenty-five years ago, the attacks of September 11, 2001, took nearly 3,000 lives. They changed countless others. We remember those killed in New York, at the Pentagon, and aboard Flight 93. We remember the families and communities who have carried that loss ever since.

We also remember the extraordinary courage of the firefighters, police officers, servicemembers, first responders, and ordinary people who moved toward danger to help others. Their heroism remains part of how we understand that day.

September 11 also changed the course of generations.

Americans came to that moment with very different experiences of war and crisis. Some still carried the memory and lessons of Vietnam. Others had served through the Cold War, the Gulf War, the Balkans, and other periods of uncertainty. They knew what it meant for the United States and its allies to act under difficult circumstances.

Many others were just beginning their careers. They were entering the military, diplomacy, intelligence, development, journalism, public service, and many other fields. For that generation, September 11 would shape much of our professional lives. For many, it would shape our personal lives as well.

We learned from one another. Those who had lived through earlier wars and crises brought experience and hard-earned judgment. Those beginning their careers brought new ideas, energy, and a deep sense of responsibility. Across generations, Americans and our allies confronted a world transformed by the attacks. They often did so under conditions of great uncertainty.

In the aftermath of September 11, the United States went to Afghanistan to pursue al-Qaeda and Osama bin Laden. It also sought to prevent Afghanistan from again serving as a base for attacks against the United States. Over time, the United States killed bin Laden. It substantially degraded the al-Qaeda organization responsible for 9/11. The sacrifices of a generation of Americans who served at home, in Afghanistan, and around the world helped prevent another mass casualty terror attack on U.S. soil for the past quarter century. Those are important achievements.

But they do not answer the larger questions raised by the twenty years of war in Afghanistan that followed the attacks.

The 9/11 Commission described its task as “looking backward in order to look forward.” Twenty-five years later, that responsibility still matters.

The Afghanistan War changed over time. American objectives expanded and evolved. Strategies changed. Successive administrations made different choices about what the United States should seek to accomplish. They made different judgments about what risks to accept and how long to remain.

Understanding those choices is at the heart of the Afghanistan War Commission’s work. So is understanding their context. We must examine their consequences. We must ask what they achieved, what proved elusive, and what lessons should be carried forward.

The human cost of that history was immense. Americans served repeatedly and far from home. Many were killed. Many more returned changed by what they experienced.

Afghans endured extraordinary loss over the course of the war. Our allies and partners also sacrificed. So did the families and communities of those who served. That sacrifice continued through the final days of the evacuation and U.S. withdrawal in August 2021.

Congress has asked the Afghanistan War Commission to examine the full course of U.S. decision-making during the war. That requires us to look carefully at how the United States entered Afghanistan. It also requires us to understand how the mission changed and why the war endured. We must examine what was accomplished and what was not. We must understand the consequences of those choices and what they can teach us about the future.

Twenty-five years later, we know a great deal about what followed September 11. We also have much more to understand.

We approach that responsibility with humility. Our task is to remember those who were lost. We must honor those who served and sacrificed. We must listen carefully to those whose lives were shaped by the war. And we must examine the choices that were made without simplifying the circumstances in which they were made.

Before the next anniversary of September 11, the Commission will deliver its final report to Congress and the American people. We hope it will contribute to a fuller understanding of the war that followed that day. We hope it will honor those who lived it, served through it, and sacrificed because of it.

And, in the words of the 9/11 Commission, we hope it will encourage our fellow citizens to “study, reflect—and act.”