WASHINGTON -- It’s been 19 years since Sept. 11, 2001, when four hijacked passenger jets were turned into makeshift missiles above American soil. But the tragic day is still fresh in the minds of some of the Army’s top leaders who survived the attack at the Pentagon.Positioned across the Potomac River from the nation’s capital, the Pentagon is the nerve center for all things national defense. It’s also one of the world’s largest office buildings, made up of roughly 23,000 military and civilian employees, including the secretary of defense and chairman of the Joint Chiefs of Staff.The five-sided structure is often seen as a universal symbol of America’s strength and security, which made it a target that September morning.As the sun rose over the nation’s capital that day, the gridlocked morning traffic crept along the Beltway. Underground, train riders like Brig. Gen. Mark S. Bennett and Maj. Gen. Paul A. Chamberlain, who were younger officers at the time, crowded into railcars to beat the slow-moving jam.All and all “it was just a morning like any other,” Bennett recalled.They were young officers navigating the city in 2001, but today Bennett is at the helm of the U.S. Army Financial Command, and Chamberlain is the director of the Army budget.By the time the Metro train dropped them off, the Soldiers weren’t the first to arrive at the Pentagon. Employees were already buzzing through each ring and corridor of the building.Pentagon staffers were already immersed in numerous morning routines; briefings were planned, PowerPoints were being finalized, coffee was brewing, and some, like Chamberlain, found time to squeeze in a morning run.“The sky was crystal clear blue that early fall morning,” Chamberlain said, looking back. “I went for a run, came back, and took a shower.” That’s when he first heard the news at the Pentagon Athletic Center. “Over the radio speakers in the shower, I heard a plane [may have] hit the World Trade Center in New York -- which was very odd.”The news quickly spread around the building. Lt. Gen. Thomas Horlander, deputy to the assistant secretary of the Army, Financial Management and Comptroller, was then a 41-year-old lieutenant colonel on a mission from Fort Rucker, Alabama that morning.The Pentagon has three times the floor space of the Empire State Building, and can be daunting to navigate for newcomers, like Horlander. The Colorado native was in an unfamiliar place during his work trip to the Defense Department epicenter.When Horlander and his coworkers walked into the building, the security guards knew they were out-of-towners, he said, during a recent interview. “I said [to the guard] we’re trying to locate a conference room. He gave us assistance and said when you get there to turn on the television -- an airplane just hit one of the Twin Towers.”After that, everything changed. Newscasts started reporting the incident at the World Trade Center in New York City. The news anchor on the confirmed “smoke was billowing out of one of the towers,” Chamberlain said. “I thought, wow, it must have been a significant plane that hit it.”‘Something is happening in New York’At first, reporters speculated why the smoke poured from the North Tower. Many anchors, like on Chamberlain’s radio, said it looked like an airplane accident. But others suggested maybe a kitchen fire from the Windows of the World restaurant, a popular tourist destination located on the 106th and 107th level of the tower. The truth was nobody knew for sure.That’s when many work routines stopped. All that people could do was watch in knots. At the Pentagon, workers, including Chamberlain, circled TVs like campfires and waited for new information like warmth. Another Army officer, Wes Miller, who was a colonel at the Pentagon in 2001, questioned if it was accident or not, he said.Before anyone could clarify what happened to the North Tower, the news broadcasted a commercial airliner fly full-force into the South Tower at 9:03 a.m., causing a massive fireball in its wake, while inadvertently confirming Miller's suspicions.“It was too unusual to see a plane fly into the side of a skyscraper. There was no way that could have been a mistake,” said Miller, who serves at the Pentagon today as the deputy assistant secretary of the Army for financial operations.As Miller watched in horror, a coworker said, “This is not a day you want to be working at the Pentagon.” The colleague planned to take leave, he said, but wasn’t able to get out in time.Attack on the PentagonMeanwhile, 64 people were onboard American Airlines Flight 77 flying from Dulles International Airport in Virginia across the country to Los Angeles. On that flight were five Saudi men, linked to al-Qaida, who hijacked the jet somewhere over eastern Kentucky.The westbound plane deviated from its flight plan, turning south at 8:54 a.m. Air traffic controllers knew something was wrong, but pinpointing AA 77 was nearly impossible. There were hundreds of planes already in the sky, each one indicated by a speck on a radar board. Roughly 30 minutes after the Twin Towers were hit, AA 77 was back in the D.C. area.The Boeing 757 airliner went full-throttle across Washington Boulevard, the expressway that separates the Pentagon from Arlington National Cemetery. The plane was flying at nearly ground-level, slicing through streetlights in the parking lot along the way.Inside the Pentagon, facing the courtyard on the first level, Horlander turned on the news from the conference room. “We were inside watching the news when we felt the building rumble,” he said. “When we looked out across the courtyard and saw a black plume of smoke, which we later understood to be from JP-8 [jet fuel],” he said.That’s when the plane’s nose pierced the first-floor façade of the Pentagon’s outermost ring, between corridors four and five, at 9:37 a.m. The deafening explosion rocked the western side of the 28-acre complex as if it were completely lifted from its foundation.“You could feel the building shake when it hit,” Miller said. “We immediately got up and started to go through our evacuation procedures. It wasn't very long before they started making announcements for anyone that had medical training. They needed individuals to come back into the building [after evacuating] and assist.”The shaking Miller felt was an 182,000-pound aircraft, still carrying thousands of gallons of fuel, colliding at full-speed into the structure. The impact punched a hole through layers of limestone, brick, concrete, blast-resistant geotextiles, and reinforced steel columns. Flames burst through the roof and reached twice the size of the five-story target.Survival and accountabilityInside the Pentagon, “they had been doing some construction above us at the time,” Bennett said, who was in the sixth corridor of the innermost ring, near the blast. Initially, Bennett’s teammates thought construction workers may have accidentally dropped something above them. But the jarring shockwave from the blast was almost too loud to rationalize.When Bennett walked into the hallway, he said, “We saw the smoke coming toward us. Smoke covered the windows. It’s not the kind of thing where a [minor construction] accident just occurred.”The impact caused the roof to partially crumble; walls collapsed, doors were blown off, and a fire burned that took firefighters days to fully extinguish. For many, it was time to evacuate. For others, it was time to contact their families.“The first thing I did was bang out a quick email to my wife [and family],” Chamberlain said. “I told them I’m fine. I’m good, but I don’t know when I’ll be able to communicate again. I love you [and] hit send.”Many communication systems were overwhelmed by greater volume than they could carry.“I tried to reach my wife, who was a federal employee at the National Institutes of Health,” Bennett said, after evacuating to the south parking lot. “The cell phones weren’t working because the system collapsed. I didn’t reach her for several hours later that day when things were restored.”From the parking lot, Bennett and another coworker spotted people they knew and jotted their names down for accountability. Keeping tabs on everyone was a demanding task, but felt instinctual, he said, especially during a catastrophic event during a time before smartphones and social media.“Believe it or not at that time, we were still using pagers,” Chamberlain said. “I sent out a quick note on the paging system and told everybody they needed to report in, and over the course of probably the next three to six hours or so, folks eventually started responding.”Like Bennett, Horlander, the out-of-towner, also evacuated to the south parking lot. But, the only thing he was looking for was his rental car. On his way, however, he helped corral individuals and calm others down, as many began to feel frantic. After leaving the Pentagon, the Fort Rucker Soldier pulled over at a bookstore and asked to use their phones.At the bookstore “we set up a makeshift [crisis response station] and contacted everyone we knew from Fort Rucker, Alabama, in the D.C. area,” Horlander said. All flights were grounded, and it was a “sobering” 15-hour drive back to Alabama in a rental van with other Fort Rucker Soldiers.The drive “left a lot of questions in our minds,” he said. “What was the future of America was going to be now that we had had an attack on the homeland?”Time answered his questions. The landscape of American culture was changed forever; increased airport security, years of war, the creation of the Department of Homeland Security, and countless other changes were ahead.Monuments were erected at ground zero in New York City; Shanksville, Pennsylvania, where the fourth aircraft crashed; and the Pentagon, where Miller, Bennett, Horlander, and Chamberlain, who continue serving today, at the Pentagon, as some of the Army’s top finance officers.Following the Pentagon attack, Miller immediately started working on finding funds in the Army’s budget to help rebuild the iconic building.The attack on the Pentagon killed all 64 people on board the aircraft and 125 people inside the Pentagon. In all, more than 2,977 people died during the Sept. 11 attacks, and more than 6,000 others were injured.“I think there's a special bond with the individuals that were here,” Miller said. “There were many others, so many I can’t go on and name them. It’s just we don’t talk about it that much, but we know that [the bond] is there.”Related linksArmy News ServiceARNEWS ArchivesDefense.gov: Pentagon MemorialVideo: Army Finance and Comptroller leaders recall 9/11 at PentagonFollow Thomas Brading on Twitter