What’s Syria capable of doing with its sarin stockpile?

A flurry of questions followed Defense Secretary Chuck Hagel’s announcement Thursday that chemical weapons — in particular, the nerve agent sarin — were used in Syria. But since no one knows how the sarin was used or who exactly used it, let’s start with the basics about Syria’s sarin stockpile.

What is sarin and how deadly is it?

Sarin is an odorless, colorless gas that’s 500 times more toxic than cyanide and deadly in doses of 0.5 milligrams and larger. If you’re exposed to it, you may begin vomiting immediately or start convulsing — or, in less severe cases, get a runny nose. Besides potentially killing you within 10 minutes of inhalation, the gas can cause paralysis and environmental damage.

How much sarin does Syria have?

Estimates vary, but as a whole, Syria is known to have the largest stockpile of chemical weapons in the Middle East and the fourth-largest stockpile in the world. Mideast weapons proliferation expert Laicie Heeley tells Foreign Policy that most estimates for the actual sarin stockpile hover around "the high hundreds of tons, possibly over 1,000."

Has Syria weaponized its sarin stockpile?

Yes. "By the mid-1990s it was estimated that Syria had developed between 100 and 200 warheads filled with sarin for its Scud-B and Scud-C missiles, and thousands of chemical bombs filled with the nerve agents VX and sarin," Dina Esfandiary of the International Institute for Strategic Studies, tells FP. "Presumably, these numbers will be higher today."

How might Syria use its sarin stockpile?

It depends. From a purely tactical standpoint, sarin is not a natural tool for the Assad regime in the context of the urban warfare it’s engaged in. "Nerve agents are effective in open spaces (battlefields) … and as a terror weapon," James Lewis of the Center for Arms Control and Non-Proliferation, tells FP. "Strategically, they are not particularly useful in urban warfare."

That’s partly because a sarin strike is unweildy, as Esfandiary explains. "Sarin in particular is very volatile (evaporates easily), which means it presents an immediate but short-lived threat," she told us. "Syria seems to have the capacity to deliver nerve gas with its rockets and missiles. But Syria’s missiles in particular are inaccurate and have small payloads. The speed at which missiles hit targets make it difficult to use them to disperse chemical weapons homogeneously."

Still, that doesn’t mean it’s useless. "The real value is as a weapon of terror; there is no bullet hole, no cut but people start twitching and dying," Lewis told us. "It is pretty haunting." Take a look at this graphic video and you’ll see what he means.

How has sarin been used in the past?

The two main cases are in Iraq and Japan. In 1995, the Aum Shinrikyo religious cult released sarin in the central Japanese city of Matsumoto, killing 11 and injuring more than 5,500. In Iraq, Saddam Hussein deployed sarin gas against his own people in Anfal and Halabja in 1988 to horrendous effect.

Why is the use of sarin a "red line" for the United States? Assad already killed 70,000 people.

It’s a good point. No one knows exactly why the Obama administration drew a line at chemical weapons as opposed to the regime’s many other nefarious acts, but arms control expert Jeffrey Lewis brings up a valuable point. "Chemical weapons use invokes an interest that has nothing to do with the future of Syria," he writes on his blog. "We have a stake in strengthening the norm against chemical weapons use. If Assad is using chemical weapons to hold on to power, we have an interest in ensuring that his government falls and that the responsible regime figures take their turn at the Hague."