LOS ANGELES, California - The inside of the building was dark, smoky, damp and hot.
It was still smoldering from the fires that raged within it just hours before, when Col. Aaron Barta, then a captain and commander of the Military District of Washington Engineer Company, and his team stepped into the battered Pentagon Sept. 11, 2001.
The company's mission was to respond to a terrorist attack in the nation's capital as a search-and-rescue team. What the Soldiers on the team soon realized was their mission would not be one of rescue, but instead, one of recovery.
Barta, who is now the commander of the U.S. Army Corps of Engineers Los Angeles District, reflected on his own personal experience as the events of that day unfolded - the day that became known as one of the worst terrorist attacks on U.S. soil.
As a young, 27-year-old company commander, Barta was listening to the radio on his way to work Sept. 11, 2001, on what he thought would be a normal day. It was Tuesday - a planned training day - and his team was poised and ready to go.
That's when Barta heard the news. A plane had hit the North Tower of the World Trade Center in New York City. At first, he thought it was a freak accident. Then, a second plane hit the South Tower. That's when he realized it was not a coincidence and the day would become anything but normal.
It wasn't until Barta arrived at work that he learned about a third plane hitting the Pentagon.
Although his team had trained for such an event - at its own facility at Fort Belvoir, Virginia, and with Federal Emergency Management Agency teams in Washington, D.C. - it had never actually had a mission like this, and Soldiers in the company weren't sure if they ever would. However, immediately after the third plane hit, the company was mobilized.
Barta traveled with the advanced team by helicopter to Fort Lesley J. McNair in downtown Washington, D.C., while the unit's main body remained at Fort Belvoir for the time being, for fear more attacks on the Washington, D.C. area were possible.
"Once we got over the horizon, above the trees, we could see smoke (from the Pentagon) coming up in the distance," Barta said.
The scene at the Pentagon was chaotic, he said, with people everywhere - trying to figure out what was going on and how they could help.
The first time the team was allowed into the building to search for victims and to assess the damage was around 2 or 3 p.m., Barta said.
"We entered through the Pentagon from the side with the other fire-and-rescue teams to do an assessment of what was in there," he said. "What a lot of people don't realize was the internal part of the Pentagon was on fire, which was raging through the building, sparked from the jet fuel (from the plane) and all of the debris. We weren't able to get in there until the fire was put out."
Not being able to get into the building immediately was frustrating, he said.
"In our minds, we had trained that we were going right into the building to do rescue operations," Barta said, "and we couldn't because of the fire.
"Not only was there fire smoldering from all of the jet fuel and the equipment, but we had a lot of broken pipes that were spraying out scalding hot water, busted sewer pipes, water from the fire trucks coming into the Pentagon ... and (the building) was still full of smoke. It was very hot in there, so we had on monitors to tell us if the oxygen was too low. In some places, we weren't able to get too far."
The team worked throughout the night.
As the Soldiers got closer to the epicenter of the disaster, various stages of what had occurred just hours before began to take shape. The plane hit on the first level of the Pentagon.
"As we walked to the second, third and fourth levels, you could see the various stages of the smoke and heat damage to the building," he said.
On the third floor, doughnuts sat on a table, uneaten, and purses were abandoned at desks, as employees had tried to flee the building.
"On the fourth floor, people had taken their coats and purses," he said. "Going to the fifth floor, it looked as if they had just closed up shop."
After 48 hours, the team's mission was changed to that of recovery. For the next 10 days after the attacks, the Soldiers, along with their counterparts, worked around the clock to methodically remove debris from room-to-room, first with shovels and wheelbarrows, and later with backhoes and machinery.
As a Soldier, preparing for events like this is something he or she trains for, Barta said, but as a human, it's not something a person could ever be prepared to see.
However, his experience during the event helped him gain a better understanding and appreciation of the capabilities of other agencies.
"It was the first time I had been put into a complex, multi-organizational problem," he said. "Figuring that out during the event helped me understand how you can take multiple organizations that had never worked together and quickly create a single work element. It also was my first exposure to the personal dynamics of human psychology and a stressful environment. I really learned - from senior leaders to people executing on the ground - how they work under stress, and I recognize those (factors). Under stress, it really comes down to human dynamics."
As he looks back on the Sept. 11 terrorist attacks, Barta described it as a wakeup call for the nation.
"The day represents a wakeup call that the world order was changing," he said. "Now it was undeniable that we have to, as a global society, reassess the definition of our values; that values, peace and those types of terms are not universal ... that was the day where people recognized that."
He also said he saw a nation become more united, with a greater appreciation for its national defense - not just military defense, but also how local emergency responders came to the nation's defense.
"We recognized the importance of the police, fire and medical personnel, what role they play and how much they put themselves at risk," he said. "I think people took them for granted (before Sept. 11). They are part of our national defense at the local levels; engrained in American values. Recognizing their contributions was probably the most significant thing that came out of it."
In memory of the Military District of Washington Engineer Company's role in the Sept. 11, 2001, recovery efforts at the Pentagon, the unit was re-designated as the 911th Technical Rescue Engineer Company Sept. 11, 2006. The company is assigned to the 12th Aviation Battalion, Army Aviation Brigade, Military District of Washington.