“GAS! GAS! GAS!”

The shouts echo up a dimly lit stairwell. Soldiers hastily wrap their faces in gas masks — the only thing protecting their lungs from a deadly, weaponized poison.

American troops are raiding a nuclear facility and they’re looking for weapons of mass destruction.

(This article by War is Boring originally appeared at War is Boring in 2015.)

The soldiers don’t know the full extent of it. But the armed occupants are using the facility as a lab to engineer chemical — and possibly nuclear and biological — weapons.

Gunfire and shouts reverberate throughout the building as the assault team moves, and as the opposition shoots back.

The Americans capture several scientists and interrogate them — as the troops try desperately to find the location of weapons and sensitive documents, all the while dodging enemy booby-traps.

Luckily, this nightmare scenario isn’t real. It’s a military training program played out on Nov. 12 as part of Gryphon Longsword — an exercise held at the never-completed Satsop Nuclear Power Plant in Washington state.

Gryphon Longsword is a joint endeavor between military intelligence, infantry, chemical warfare, and Special Forces troops based at Joint Base Lewis-McChord. The focus is on learning how to fight and work together in a contaminated environment.

Despite the bloody invasion of Iraq to shut down Saddam Hussein’s non-existent weapons of mass destruction program, the issue of chemical, biological and nuclear proliferation is still very much on the Pentagon’s agenda.

In 2006, North Korea became a nuclear-armed state after a successful weapons test, and Pyongyang since declared it’s producing nuclear warheads. The United States has also accused Iran of developing nuclear weapons under the guise of a domestic energy program.

On Aug. 21, 2013, the Syrian regime of Bashar Al Assad killed hundreds of people with Volcano rockets packed full of sarin, a deadly nerve gas.

With all these weapons out there, the Army wants its soldiers to be aware of the unique dangers of operating in an environment where an enemy could use these weapons against them.

The soldiers in the exercise admit they don’t know whether they will encounter a scenario like this, but they also can’t be sure they won’t.

Battling inside a nuclear reactor

Construction of the Satsop Nuclear Power Plant began in 1977. It was to be the largest nuclear power project in American history. The site was 75 percent complete in 1983 when the money ran out.

By then, American public opinion had swung sharply against nuclear power after the Three Mile Island disaster. The state decided not to fund the project further, and the site remained unfinished.

Thirty years later, the area is now a business and technology park in the shadow of two massive, inactive cooling towers. But the site, killed by America’s fear of nuclear power, found new life thanks to America’s fear of nuclear and chemical weapons.

Since 2005, the Army has used the site to train soldiers for operating in hazardous environments — and for learning how to clear buildings room to room. Gryphon Longsword focused on the complex’s large reactor building.

The labyrinth of hallways, stairs and rooms snake deep under ground — an ideal environment for ambushes. The corridors of the facility look like a level from Half-Life. It’s incredibly difficult to navigate. And that’s why the Army loves it.

“It forces soldiers to think,” says Lt. Col. Justin Haynes, commander of the 502nd Military Intelligence Battalion.

His soldiers are among those taking part in the exercise. “It’s not like anything they’ve seen before.”

Before helicopters arrive to drop off the assault teams, soldiers at the site adopt the role of civilians and the armed opposition. They set traps and plant documents — critical intelligence items the attacking soldiers will need to discover to learn about what’s happening inside the facility.

Civilian scientists play an important role in the exercise. According to the scenario, the enemy guards are forcing the scientists to produce weapons against their will — and the guards have already killed several scientists for refusing.

At first, the cartoonishly evil villains makes the situation seem a bit simplistic, but it really makes the scenario far more complex. The soldiers need to take extra care not to kill the potentially helpful scientists. Many of them have valuable intelligence. It’s important for the soldiers to avoid going into every room with guns blazing.

Chief Warrant Officer Christopher Dawson of the 555th Engineer Brigade’s 110th Chemical Battalion helped set up the exercise. He’s also there to observe the training and dispense advice.

“We’ve never done this before,” he says, as he and other soldiers wait for the helicopters to drop off the first batch of attacking troops.

He explains that joint operations involving chemical troops, regular infantry and military intelligence are rare. Getting so many soldiers with different specialties and jobs to work together well in the same space is a challenge.

“Sounds like a cluster to me,” one sergeant remarks.

“That’s why we’re doing this” Dawson replies. Making something like this work takes practice.

As Chinook helicopters land, soldiers immediately get out and start securing the facility, beginning with several nearby buildings. They search for weapons, detain and question a few suspects, and then move closer to the reactor.

During a firefight with a group of opposition troops, the soldiers see smoke. They don’t know if it’s coming from a smoke grenade or a chemical weapon.

The soldiers need to be constantly mindful of the direction of the wind. Dawson explains that in a chemical environment — where a change in wind can mean gas blown toward a friendly troop formation — paying attention to such small details is the difference between living or dying.

As the soldiers move into the main building, the exercise becomes increasingly chaotic. It’s dark, so the soldiers must rely on flashlights. They move carefully down creaky, pitch-black metal stairways.

After the infantry clear the rooms and capture guards and scientists, the intelligence troops pick through objects and begin interrogations.

As the assault teams move deeper into the facility, they discover their radios are no longer reliable. They’ve brought a telephone with a long cord to communicate in the facility, but they largely depend on runners to relay information.

Lt. Col. Jeff Bryson, the battalion commander of the infantry troops, observes the exercise. He has a scowl on his face.

He notices group of soldiers watching another team go down a stairway.

“I see a lot of people just standing around,” Bryson shouts.“Lets try pulling security, you know? Like you’re in the Army!”

As the soldiers reach the bottom floor, the enemy troops — clad in protective chemsuits of their own — release a cloud of gas. The soldiers put on their gas masks. The gear diminishes visibility and makes verbal communication much more difficult.

For the soldiers, it’s disorienting.

Muzzle flashes illuminate the dark hallways as soldiers make their way forward, clearing rooms as they go. They find an animal testing room and a lab for producing nerve gas — and they capture several scientists.

Although simulated, the fighting is fierce. The temperature is near freezing, but the soldiers are boiling in their heat-trapping protective suits.

Staff Sgt. David Kinsler triggers a trap near the end of the exercise, as other soldiers capture the chief scientist. Kinsler and a fellow soldier are the final casualties.

He says he’s accustomed to training in much simpler settings, with walls made of plywood and makeshift materials. The large facility is a big change for him. Kinsler also notes he hasn’t worried about wearing a chemsuit and gas mask in more than a decade.

“I haven’t cleared in a full chemsuit since 2003,” he says.

Kinsler fought in the initial invasion of Iraq.

Chemicals in the real world

When the U.S. invaded Iraq in 2003, the Pentagon told commanders to be ready for anything — from radiation to deadly nerve agents. The soldiers of the expeditionary force wore protective suits to shield themselves from poison gas, nerve agents and bio weapons.

They donned gas masks as they searched suspected WMD caches. It was an absolutely miserable way to fight a war in the desert.

They did find scattered chemical and biological shells as they secured some Iraqi facilities. The problem is that none of them were part of any active weapons program — the main justification for the entire war.

They found nothing to suggest any active, large-scale program. As American troops moved into Baghdad and secured surrounding areas, the soldiers stopped wearing their protective gear.

But in October, New York Times reporter C.J. Chivers revealed that American troops in Iraq found chemical weapons on a much wider scale than previously reported. U.S. forces encountered thousands of chemical and biological munitions.

Many were American-designed weapons, produced in Europe and exported to Iraq to fight Iran on the West’s behalf.

At that time, Western states actively helped the regime obtain and produce chemical weapons. Hussein used these weapons both against the Iranians, and against his own people to quell uprisings. Ba’athist forces used these weapons in the massacre of the Kurdish town of Halabja, the single most lethal chemical weapons attack to date.

Showing the world those weapons would have been an embarrassing reminder of a chapter of history the Pentagon — at the time headed by Donald Rumsfeld, a central figure in U.S.-Iraqi relations during the Reagan administration — didn’t want to discuss.