Americans today tend to have a short attention span. Important news often is quickly overshadowed by the latest nonsense posing as news that captures the nation’s attention.

Yet some events are of such a magnitude that they remain seared in our memories. The attack at Pearl Harbor. Troops storming the beaches at Normandy. The fall of Saigon. And the events of Sept. 11, 2001.

For those old enough to understand what was happening 23 years ago, when terrorists hijacked four planes — two of them brought down the World Trade Center, one smashed into the Pentagon and the fourth crashed in a field in Shanksville, Pennsylvania — those events will forever be imprinted in our minds.

But for many younger people, 9/11 is a vague recollection of events that seemed to shock adults around them to the core. For even younger Americans, the attack on our nation is mere history.

Most of them are too young to remember how Americans came together to “Never forget.” They don’t know the horror of learning nearly 3,000 people were killed because violent extremists used their religion and political ideology to justify an attack on freedom. They don’t know how it felt to watch a nation come together and declare that what we stood for was worth protecting and that we made that declaration as one people.

So today, as we look two-plus decades into the past to one of the most terrifying moments in American history, we must never forget what it is about this nation that so infuriated those who sought to destroy us. We must never forget those who died. And we must never forget the nearly 4,600 U.S. servicemembers killed in the Iraq war and 2,500 killed in Afghanistan.

At a time when it feels as if politics is driving a wedge between Americans, we must always remember we are, still, the United States of America. We are united once again by the vow that while we may be different, we are indivisible, that we are one nation, under God. That, we must never forget.