It was with more than a bit of relief — and perhaps some amount of surprise — that Americans awoke on the morning of Sept. 12 to the realization that the 10th anniversary of the attacks of Sept. 11, 2001, had passed without a long-feared reprise by al-Qaida or other terrorist groups.

The national level of fearful anticipation had been raised by warnings from the Department of Homeland Security of a “credible but unconfirmed” report that as many as three potential attackers, including two who possibly were American citizens, were threatening to attack commemorative events in New York City or Washington, D.C.

As a result, police and military forces were visible everywhere on the streets in both cities, with security especially strong near the Capitol, the White House and the Pentagon in Washington and the National September 11 Memorial (no longer to be called “ground zero” since its dedication on Sunday) in New York.

Cars and especially trucks were searched, and fighter jets kept on alert in case of highjackings. A pair of false alarms did set heartbeats racing, when F-16s were scrambled to escort an airliner in which passengers entered a rest room and failed to emerge after a long period of time.

It turned out that the reasons involved romance, not terrorism, but their irresponsibility (and poor choice of days) made them the objects of considerable concern for a time.

Another jet on which passengers were “acting strangely” also earned a fighter escort, and an airport in Missouri was closed for a time when a prospective passenger refused to allow luggage to be inspected. The bag did not contain explosives, but the recalcitrant flyer was detained by police.

Nevertheless, none of those incidents interfered with memorial ceremonies in New York, Washington and in the rural Pennsylvania town of Shanksville, where United Flight 93 was brought down by its passengers before its highjackers could attack the U.S. Capitol, its intended target.

Great thanks and honor are due all those, in uniform and out of it, government workers and civilians, known and unknown, who have protected our nation since 9/11 and whose efforts have intercepted and halted a number of plots and potential attacks in the decade since.

Their efforts permitted a day of sorrow and remembrance to proceed unmarred by further violence; they continue to guard us today and will do so in the days and years to come.