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No, ISIS isn’t gassing US troops in Iraq

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An old gas mask in Belarus.
(Sean Gallup/Getty Images)
Zack Beauchamp is a senior correspondent at Vox, where he covers ideology and challenges to democracy, both at home and abroad. Before coming to Vox in 2014, he edited TP Ideas, a section of Think Progress devoted to the ideas shaping our political world.

Last week, the Pentagon announced something disturbing: ISIS tried to use chemical weapons against US troops in Iraq.

Tests of a rocket or mortar shell fired against a joint US-Iraqi air base "returned a positive test for a mustard agent," the Pentagon said. No US troops showed signs of having been affected by the chemical agent.

Despite the fact that no one was injured, this sounds really scary. It conjures up images of the horrors of World War I, where both sides gassed each other, and raises the dark prospect of the American troops who poured into Iraq in search of Saddam Hussein’s weapons of mass destruction now running the risk of being hit by chemical weapons fired by the Islamic State.

But, it turned out, it was wrong. Late Tuesday afternoon, the Pentagon reversed itself. Air Force Colonel John Dorrian, the spokesman for the counter-ISIS coalition, revealed that "definitive" tests found "no mustard agent present" in the munitions fired at US troops.

This points to a broader point, one hammered home by experts on ISIS and chemical weapons: The Islamic State’s group’s chemical weapons capability is extremely limited. The type of weapon ISIS was suspected of using extremely primitive, in some ways less dangerous than a simple artillery shell — underscoring the fact that hyping ISIS’s chemical weapons would be a huge mistake.

What mustard really is

Imperial War Museum Prepares Sargent's Gassed Painting For US Tour
A painting depicting the use of mustard agent during World War I.
(Rob Stothard/Getty Images)

The first thing to understand about mustard, so named because impure versions smell kind of like the condiment, is that it isn’t actually a gas. It may become one, but the version used in military operations starts out as a kind of viscous, oily liquid.

Back in World War I, when it was first used in large quantities, warring parties would spray it out from big water tanks. They would also put it in shells fired from artillery pieces, which would then explode and send gobs of the liquid onto the exposed skin of enemy troops. Think of it like a really dangerous water balloon.

That’s what ISIS allegedly tried to use on Tuesday, but it turned out they didn’t. So panicked media reports — like this item in National Review warning of dire consequences if America ignored this incident and ISIS’s chemical weapons —were extremely premature.

Regardless, the Pentagon believes ISIS does have some mustard gas, and it’s certainly nasty stuff.

When it comes into contact with human skin, it causes extremely painful chemical burns. Those are rarely fatal, making mustard relatively less lethal than other weaponized chemical agents like sarin. From a sheer survival standpoint, you’d probably rather be near a mustard bomb than a conventional high explosive.

Mustard gets more deadly when it begins to evaporate. When that happens, people inhale the chemical — which means the burns happen on the inside of their bodies. This causes a deadly fluid buildup in the lungs, and people drown to death even when they’re standing on dry land.

That sounds, and is, pretty horrible. But it takes a lot of mustard to wound or kill significant numbers of enemy forces.

"It’s not a single shell or rocket or bomb that would achieve that," Dr. Jean-Pascal Zanders, the former chemical and biological weapons project leader at the Stockholm International Peace Research Institute, explains. He then recited some figures:

To saturate one square kilometer of terrain with mustard agent and kill 50 percent of the people inside without protection, you would need 20 tons of agent per hour...the comparative figure for sarin is four tons.

Figuring out how to amass and use that much mustard is so impractical, Zanders says, that "nobody would do that." Instead, mustard is more commonly used to deny territory to enemies or to force a civilian population to evacuate. You drop a bunch of mustard somewhere, and it becomes difficult for troops to cross without having to take serious and time-consuming precautions like donning gas masks or full body protective gear.

So even if ISIS had actually fired a single shell with something that may-or-may-not have mustard in it, it’s not significantly more dangerous than them firing a simple rocket. There’s no reason to hype it up just because mustard is a chemical agent.

ISIS’s chemical weapons are more about psychology than military value

ISIS Propaganda
Much like this ISIS propaganda video.

Nonetheless, the not-actually-mustard shell got headlines. That’s due to the unique psychological nature of chemical weapons: Because we find them to be much more terrifying than conventional weapons, ISIS using one — even though it failed — is more panic-inducing than even a successful strike using rockets, mortars, grenades or other types of run-of-the-mill armaments.

This is why the Bush-era term "weapons of mass destruction" never made any sense. A chemical weapon like mustard agent is less dangerous than a weaponized biological agent like smallpox, which is in turn way less dangerous than a nuclear bomb.

"Re WMD, how can one acronym include both a lone mustard shell and a nuclear warhead?" CJ Chivers, the New York Times’ excellent military correspondent, tweeted. "It's arguably the worst acronym in discussions of war."

And from what we’ve seen so far, ISIS’s "WMD" capabilities just aren’t very dangerous. In addition to mustard, they’ve also used chlorine bombs — a very primitive chemical weapon made from a common cleaning supply.

"These are very crude chemical weapons," Daveed Gartenstein-Ross, a senior fellow at the Foundation for the Defense of Democracy, tells me. "The chemical weapons they’ve been most successful with, chlorine-based CWs — they’re not on the scale of mustard."

So based on what we’ve seen so far, there’s no evidence that ISIS has a major stockpile of chemical weapons raring to go.

"[If] it’s the tip of the iceberg," Gartenstein-Ross says, "it should be understood in the context of a world where there’s been massive climate change, so icebergs aren’t what they used to be."

That’s not to say that ISIS’s chemical is totally pointless. The smart money is that they’d use it to buy time.

The US and its Iraqi allies are gearing up for an offensive on Mosul, Iraq’s second-largest city and the crown jewel of the ISIS empire. ISIS’s chemical capability forces the coalition to prepare for CW by stocking up on hazmat suits and gas masks, slowing down the offensive.

"I think we can fully expect, as this road toward Mosul progresses, [ISIS] is likely to try to use it again," Navy Capt. Jeff Davis said, per "They are dead set on it."

This wouldn’t change the strategic calculus; the US and its allies would still be far more powerful than ISIS. But it would help the group at the margins — and, given its dire strategic position in the Middle East, they’ll take what they can get.