Twenty-five years ago, I had just returned from a conference in Austria when several European friends left me with an unsettling warning: the terrorist threat against America was extraordinarily high.

Their concern stayed with me. For several years I had written and spoken publicly about Islamist terrorist organizations and the danger they posed, particularly in the Middle East and to Israel. I had said more than once that it was probably only a matter of time before America itself became the target of a major attack.

I had no idea that time would come on a beautiful Tuesday morning in September.

At 9:00 a.m. on September 11, 2001, I was conducting a policy staff meeting at Family Research Council’s media center in Washington, D.C. I was FRC’s vice president for Policy and had become a well-established media voice on national security and foreign affairs.

Shortly after our meeting began, then-FRC Vice President Doug Werk entered with startling news: an airliner had struck one of the World Trade Center towers.

None of us understood what that meant. Minutes later, I heard a distant explosion. Soon sirens filled Washington. Word followed that the Pentagon had been struck.

The United States was under attack.

I dismissed my staff and hurried upstairs, where television revealed the enormity of what was unfolding. We watched aircraft plunge into the towers and saw smoke rising from the Pentagon a few miles away. People poured into the streets as offices across Washington released their employees. No one knew whether the four hijacked airplanes were the entirety of the assault or merely the opening blows of something larger. That uncertainty is hard to convey to those who did not live that morning. We know the history now. We did not know it then.

I remained in my office. Because I had spent years writing and speaking about terrorism, media organizations began calling. Interview followed interview. By the end of the day, I had conducted 31 media interviews, including three appearances on Fox News extending late into the evening.

Eventually I headed home before returning that night. What I saw on the drive remains etched in memory. Interstate 395, normally choked with rush-hour traffic at 5:30 in the afternoon, was virtually empty. As we passed the Pentagon, the building was still burning. I had spent the day explaining terrorism to others, but nothing I said on television could capture the sight of the wounded Pentagon against the evening sky.

And 9/11 did not end for me that night.

In 2002, after nine years at FRC, I returned to full-time work at the Pentagon with the Department of the Army, where I saw firsthand the opening years of what became decades of conflict with jihadist terrorist organizations. My subsequent work took me into war zones and close to many of the national security consequences unleashed that September morning.

The physical reminders were always nearby. I visited the Pentagon Memorial Chapel, built where American Airlines Flight 77 tore into the building, and frequently walked the adjacent Pentagon Memorial grounds, which honor the 184 people killed at the Pentagon and aboard Flight 77 that morning. I also visited and spoke at the Flight 93 crash site near Shanksville, Pennsylvania, where passengers and crew fought their hijackers before the aircraft went down in a field rather than reach its intended target. Twice I traveled to Guantánamo Bay, where the legal aftermath of America’s struggle with al-Qaeda remains visible even today; military-commission proceedings tied to the September 11 attacks continue a quarter-century later.

That history is why this year’s controversy surrounding New York City Mayor Zohran Mamdani’s (D) participation in the 25th anniversary observances deserves careful treatment.

Mamdani’s chief counsel at City Hall is Ramzi Kassem. Before entering City Hall, Kassem spent years representing detainees held in the post-9/11 war on terrorism, among them Ahmed al-Darbi. Al-Darbi pleaded guilty in 2014 to war-crime charges tied to an al-Qaeda attack on the French oil tanker Limburg, and he was also the brother-in-law of Khalid al-Mihdhar, one of the hijackers aboard Flight 77.

That history has angered some 9/11 families. This week, relatives delivered a petition to City Hall asking Mamdani not to attend the Ground Zero ceremony; others have rejected efforts to exclude him, arguing the memorial should stay free of partisan conflict. Mamdani has said he intends to attend.

Fairness requires more. Representing a defendant — even one convicted of terrorism — is not the same as endorsing his ideology or crimes. Kassem has said that on September 11, 2001, he was a law student in New York who tried to locate friends at the World Trade Center, donated blood, and volunteered with the Red Cross helping callers seeking relatives. Mamdani, for his part, has signed executive orders establishing September 11 as a New York City Day of Remembrance and Service and strengthening the city’s emergency-continuity planning, calling for a citywide moment of silence honoring both those killed on September 11 and those who later died from illnesses tied to the attacks.

Those facts belong in the record too. But they do not erase the deeper question raised by this anniversary: What does it mean to remember?

For those of us who experienced September 11 firsthand, remembrance is not an abstraction.

I remember the warning from Europe. I remember Doug Werk walking into our meeting. I remember the distant explosion. I remember the sirens. I remember wondering whether more attacks were coming. I remember 31 interviews while Washington emptied around me. I remember an abandoned I-395. And I remember the Pentagon burning.

Then came the years afterward — the Pentagon chapel, the memorial, Shanksville, Guantánamo, war zones, fallen Americans, wounded warriors, and a struggle against terrorism that lasted far longer than anyone imagined that September morning.

The argument over who attends a memorial ceremony should never outweigh the people being remembered there. September 11 belongs first to the nearly 3,000 innocent people murdered, to their families, to the First Responders who ran toward danger, and to those who later sacrificed in defense of this country.

Public officials who enter those places of remembrance carry a special responsibility. They walk on ground made sacred by sacrifice and grief. Whatever their politics, they should approach it with humility.

Twenty-five years have passed. For some Americans, 9/11 has become history. For many of us, it remains memory. And there is a difference.