9/11 -- 11 years later: A nation pauses to reflect and mourn anew NEW YORK -- With bagpipes and somber bells sounding a sharp counterpoint to the commemorative moments of silence, the nation on Tuesday marked the 11th anniversary of the terrorist attack that brought down the World Trade Center in Manhattan and shattered the country's political psyche. At ceremonies in New York, at the Pentagon and in Washington, relatives and friends mourned the victims of the Sept. 11, 2001, attack by Islamic terrorists. The scenes were as moving as those from previous ceremonies, though they also seemed more personal than in the past, especially compared to last year's 10th anniversary. Unlike past events, authorities did not raise any special security alerts this year. The sun rose on a cool, crisp morning, remarkably similar to that which dawned 11 years ago. At all three sites -- the National September 11 Memorial & Museum in Manhattan, the Pentagon, and a field in Shanksville, Pa. -- the focus was on the victims who died when terrorists hijacked four commercial jetliners. The Manhattan ceremony also honored the six people killed on Feb. 26, 1993, when attackers set off a truck bomb beneath the North Tower of the World Trade Center. PHOTOS: Commemorating the 11th anniversary of 9/11 A total of 2,983 people died in the 1993 and the 2001 attacks, the latter of which brought down both World Trade Center towers. As in past years, the day in New York began with a bagpipe procession, followed by an honor guard and the reading of all the victims' names in alphabetical order by relatives, who often added personal messages to their recitations. Your family and friends miss you. We will never forget, Johnny," Martin Collins said to his brother, New York firefighter John Michael Collins. Listeners clutched flowers and photographs of their loved ones as husbands, wives, sisters, fathers and other relatives took turns at a microphone to read each name aloud. Six moments of silence marked the ceremony: four to note the moments when each jet crashed, and two to note the moments when each World Trade Center tower fell to the ground. Now, the footprint of each tower is filled with a giant reflecting pool, and the names of victims are etched into bronze parapets, allowing visitors to run their hands over the names as they peer into the watery voids. There were no political speeches in New York, and this year's presidential campaigns were briefly paused. Both campaigns pulled some negative ads in a bow to the somber ceremonies. Political overtones nonetheless But both candidates were highly visible. President Obama and his wife, Michelle, observed a moment of silence on the White House lawn at 8:46 a.m. Eastern, the moment the first hijacked plane crashed into the World Trade Center. The Obamas then went to the Pentagon, one of the other targets of the Al Qaeda attack. There, the president -- aided by a Marine honor guard -- placed a white floral wreath on a metal stand above a concrete slab that read "Sept. A moment of silence began at precisely 9:37 a.m., when United Flight 77 hit the west side of the Pentagon 11 years ago. One hundred and eight-four people died that day. Both Obama and Defense Secretary Leon Panetta stressed that the United States is stronger today because of how it has fought back against terrorists around the world, including in Yemen and north Africa. It was on Obama's watch that U.S. forces killed Osama bin Laden in Pakistan, a point frequently made by Democrats during the current presidential campaign. Obama said the United States is safe and its people more resilient than on the day of the attacks. "No matter how many years pass, no matter how many times we gather on this hallowed ground, know this -- you will never be alone," Obama said in televised remarks. Your loved ones will never be forgotten. Obama then went to Arlington National Cemetery in Virginia, just outside Washington, D.C. Romney was at Chicago's O'Hare Airport, where about two dozen firefighters gathered on the tarmac for a brief memorial timed to the moment the first plane struck the World Trade Center. Standing on and in front of several fire trucks, lights flashing, the firefighters stood at attention, saluting, for a full minute at 7:46 a.m. Central time. A large American flag was draped on the trucks behind them. Romney arrived at the airport for a campaign flight about 15 minutes later. Before boarding his plane, he strode about 100 yards across the tarmac to where the firefighters were still gathered in a row and shook hands with each of them. "On this most somber day, those who would attack us should know that we are united, one nation under God, in our determination to stop them and to stand tall for peace and freedom at home and across the world," Romney said in a written statement distributed by the campaign. Vice President Joe Biden attended the ceremony in Shanksville, Pa. It took place before a white marble wall with the names of the 40 passengers and crew from United Flight 93, forced to crash in the field by the heroic passengers and crew on the hijacked plane. The names of the dead were read aloud with two bells sounding each time.