It's been 20 years since that tragic day in 2001. But to most of us it seems like yesterday.
That terrible morning when four U.S. jetliners were hijacked by terrorists we soon learned were part of Osama bin Laden's al-Qaeda network.
Nearly 3,000 people died in the attacks. And life for the rest of us changed forever.
We were shaken. We were frightened. We were outraged. But most of all we were united. We were determined nothing like this would ever happen again.
President George W. Bush was a commanding presence in the weeks after the attacks. He provided strong leadership, reassured the country and vowed to crush al-Qaeda and hunt down its leader no matter where he tried to hide.
Our troops and allies reduced al-Qaeda to a shell of its former self. And it took almost 10 years. But Osama bin Laden paid for his crimes.
Nothing could ever bring back those who died September 11. Nothing could truly comfort their loved ones. But at least they received a measure of justice.
Today, we don't know what the future holds for our national security. The fall of Afghanistan to the Taliban presents the very possibility that al-Qaeda or aligned terrorist organizations might use that country as a base to stage a comeback. Perhaps even launch another attack on U.S. soil.
And now we face the prospect of such groups using sophisticated cyberterrorism as well.
So we must be vigilant. We must be ready. The threat is still out there.
And we must never forget the lives lost and lesson learned on September 11, 2001.