(Editor’s note: This is an updated version of a commentary I posted several years ago around the anniversary of 9/11.)

Has it really been 25 years since the September 11 attacks? Consider this: Nearly half the U.S. population—45 percent—was either not yet born or too young to remember when the World Trade Center towers burned and collapsed, when a hijacked plane crashed into the Pentagon, and when Flight 93 crashed near Shanksville, Pennsylvania.

Perhaps for them, and for those who come after them, 9/11 will be what Pearl Harbor was for older Americans. Growing up, I knew well the significance of December 7, the image of the USS Arizona listing badly as thick black smoke poured from the ship, and the immortal words of President Roosevelt declaring that the date would “live in infamy” because of the news stories on the anniversary and the stories my parents told.

But the event was not burned into my consciousness as it was for my parents. For them, Pearl Harbor and World War II were defining moments, forever changing the course of this country and its people. Victory came at great cost, but it also established America as a world power and a primary guardian of freedom.

It is often said that 9/11 was our generation’s Pearl Harbor—a contemptible attack on unsuspecting people, designed to shake the country to its core and cause Americans to question their place and their duty. The country passed that test 82 years ago, but we still do not know how history will ultimately judge the post-9/11 era.

As columnist Robert Samuelson said after 9/11, perhaps this is not a war we are in, but rather a permanent condition. We may be able to root out those responsible for individual attacks, but we cannot expect to eliminate the threat of terrorism for all time. For terrorists, there will always be new generations of recruits and new grievances.

At least our parents and grandparents were able to witness the destruction of their country’s enemies and the cessation of hostilities. There were no half-measures. A full and unconditional commitment to the effort ultimately led to victory and peace.

We still do not know if—or when—that will happen in a post-9/11 world. How does one fight and win a war against a continuous terror threat? What are the markers that define victory or defeat? What sacrifices must be made in order to prevail?

We know that we must remain committed. As the military strategist Carl von Clausewitz said, “The minute we begin to carry out our decision, a thousand doubts arise about the dangers which might develop if we have been seriously mistaken in our plan. A feeling of uneasiness, which often takes hold of a person about to perform something great, will take possession of us, and from this uneasiness to indecision and from there to half measures.”

That is a fair warning about what may lie ahead, even 25 years after the attacks. However, we should also be grateful that the security measures put in place since 9/11 have helped prevent another similar attack on American soil.

No rational person would wish to return to the time just after 9/11, yet it is undeniable that a wounded America pulled together. For a moment, at least, we pushed aside our differences and focused with laser-like intensity on what we shared as Americans and on a common purpose.

Over time, wounds begin to heal, differences inevitably resurface, and a sense of normalcy returns. But September 11 is still there—a permanent fixture of our national identity that, when we pause to remember, reminds us of our generation’s calling to preserve, protect, and defend our great nation.