"Fall in!" shouts a terse Air Force Sergeant pulling the evening duty shift together at the base of operations for the 55th Security Squadron at Offutt Air Force Base.
The diverse group men and women lining up in tight formation have the no-nonsense air of people you don't want to mess with. It's a mix of both Air Force and Navy personnel. That reflects the presence of the base's highest-profile component: the headquarters of the United States Strategic Command. It's here that the nation's nuclear arsenal, ready on land, sea and air, is coordinated.
They listen at attention as their leader tells them "we are currently in BaseCon Alpha with select Bravo measures," which means nothing unusual in their security routine as the shift begins. Back when they were being trained, they got some stern advice about nights like this from long-timers like Staff Sergeant Jason Winkle.
"Always be ready," he tells them. "You never know what's going to happen (or) when it's going to happen. Train like you fight and you'll be fine."
It's the most important lesson he and others walked away from while on duty on September 11, 2001.
Their duty officer breaks up their formation, barking out, "Flight, attention! Post!" and they head off to make their rounds.
This is a new era in security on America's military bases. Air Force Security Forces Training now lasts 65 days, almost a full week more than was required prior to 2001. The intensive course teaches everything from and recovery of nuclear weapons to using pepper spray.
"The course was lengthened post-9/11 to make sure the security forces had all the skillsets they needed to do the job they're doing," Lt. Col. Mike Kelly, 343rd Training Squadron commander, told the Air Force News Service.
On a muggy July afternoon, Technical Sergeant Tim Cross made his afternoon rounds, ready to address anything from a routine traffic accident to a security breach.
Driving in his security vehicle and between radio transmissions he told NET News, "The training I've received has been goodm meaningful training that will actually help us counter-react to a terrorist situation."
On the other side of the base, in a bland, sand-colored garage, a half dozen stone-faced security officers in military camouflage with an impressive arsenal work their way through a plywood mock-up of an office complex, taking instructions by walkie-talkie. They're in a training exercise simulating an "active shooter" on base.
A crackling voice advises the armed team called "Delta One" that "medic have been notified" just as simulated gunfire erupts. They burst through the door of the office, weapons drawn, and take down the "shooter."
The layout of this fake office is unique: It mirrors the floor plan of the highly secure underground command center of the United States Strategic Command, where nuclear weapons are controlled.
Security trainer Winkle explains that this sort of training plays "a huge part" in how a real situation could unfold for security officers - in other words, if someone will live or die.
"The more people you can get inside," he said, "the faster you can take care of the active shooter (and) the fewer people will get hurt."
To an observer, that seems more like police SWAT team work than a response to terrorism. However, everyone in U.S. military security learned important lessons in 2009 when Maj. Nidal Hasan shot and killed 13 fellow soldiers and 32 others at the massive Fort Hood army base in Texas. That was labeled an act of domestic terrorism by prosecutors.
In the ten years since he worked as a security officer the day of the September 11 attacks, Sgt. Winkle became part of a culture of hyper-concern about security at Offutt Air Force Base.
"Everything changed," Winkle told NET News. "Our whole mindframe, the atmosphere. Everything changed. You come to work, the job you do is important, and that's what people had to come back to and realize - that we have an important job to do."
Cross remembers what that day was like.
"We all put our gear on. Helmets. Protective armor. We just didn't know what was out there and our base could be a potential target," he said, admitting he was "very nervous. I think it's that fear of the unknown."
That day, the job of every security officer on base changed dramatically. It shows the minute you arrive at Offutt's front gate. Without the proper identification card, no one just drives on base anymore. Every single car gets stopped, at least briefly. That's a big change from ten years ago.
"(Pre-)9/11 you would just have the little sticker, they would wave you on in and then you could go park," recalled Patricia Nekuda, a civilian employee working as mailroom supervisor at the Strategic Command headquarters. Visitors not working at the base must stop, get out of their car, register, and be escorted onto base.
That's still a step down from the frightening level of armed security they faced the first few weeks after the terrorist attacks. Nekuda remembers her first day back on base.
"We come through the gate, and they had a .45-caliber (gun) pointed at the people coming onto the base. In my mind I'm going, 'Those are loaded!'" she said. "There's no more games. There's no more exercises. This is for real."
According to the man who coordinates security on base, Offutt has one of the busiest visitor control centers in the Strategic command.
"That's why we do 100 percent ID checks and some background checks on everyone coming into the installation,"
Chief Master Sergeant L.D. Retelle of the 55th Wing Security Squadron told NET News.
One major change since 9/11 is to not let his security teams fall into predictable patterns, he continued.
"We do what we call random anti-terrorism measures," Ratelle said. "Every now and then we'll check everyone in the car, not just the person holding the ID card, and do a 100 percent check."
That can include using the National Instant Criminal Background Check System maintained by the FBI to check for any outstanding arrest warrants a base visitor might have. He said it's important "just to see their need to come on the installation. It's pretty robust."
It's Offutt's goal to have everyone on base, whether on the security force or not, to take responsibility for safety. Take Heather Jackson, who works at the base medical clinic. Since 9/11, she said she knows that even as a civilian worker, security is no longer just up to the uniformed patrols.
"You don't take for granted, and you don't turn the other way as easily, when you see something that just isn't quite right," she said. "If something in your gut is telling you something is not right, you're most likely correct."