A decade later

Americans will observe today's 10th anniversary of the heinous strikes against this country under the threat of new violence. The U.S. Department of Homeland Security announced Thursday that it was investigating a credible tip that al-Qaida intends to launch another Sept. 11 attack.

The alert is a reminder of the cruelty and resolve of our enemy. But it is also a reminder that innocent civilians remain the prime target of terrorists, and therefore the most likely to see an attack unfold and do something about it.

Let us never forget the brave passengers of United Flight 93, who 10 years ago today took the fight to their al-Qaida hijackers, crashing the Boeing 757 into a Pennsylvania field before it could reach the Capitol or the White House.

Let us remember, too, the crew and passengers who prevented Richard Reid from downing an American Airlines flight with a shoe bomb in December 2001. Same for the civilians who subdued Umar Farouk Abdulmutallab when he tried to crash a Northwest Airlines flight over Detroit on Christmas Day, 2009, with a bomb sewn into his underwear. Recall the alert citizens who stopped attempted car bombings in New York in 2010 and London in 2007.

So as we mourn the nearly 3,000 people who were killed by al-Qaida 10 years ago today, let us also remember the carnage of terrorist attacks carried out against innocents in London, Madrid, Bali and Mumbai in the years since.

The Islamic fanatics who carried out these attrocities despise our freedoms and all the prosperity that results from liberty. We are a free people, and as long as we resist the smothering tactics of a police state, there will be inviting vulnerabilities for those who wish us harm. Police can only cover so much ground.

Which makes it even more vital a decade after 9/11 that we -- as a nation and individuals -- remain ever vigilant.