Syria’s President Had Stocks of Chemical Weapons. What Happens to Them Now?

Rebels seized control of Syria’s capital on Sunday, ending the reign of Bashar al-Assad, who infamously used chemical weapons to kill thousands of his own citizens during the country’s 13-year-long civil war.

Now, a militia group that once had ties to the Islamic State and al Qaeda, before renouncing them in 2016, is in control of Damascus and, presumably, what is left of Mr. al-Assad’s arsenal, prompting concern in the United States and elsewhere that the chemical weapons could fall into the wrong hands.

Here is what you need to know about Syria’s chemical weapons.

What is Syria’s history with chemical weapons?

Mr. al-Assad’s use of chemical weapons on rebel groups and civilians was a defining feature in the early days of Syria’s civil war, so much so that in 2012, then U.S. President Barack Obama warned that their continued use would cross a “red line” that would justify U.S. military intervention.

Mr. al-Assad ignored the warning, and on Aug. 21, 2013, he launched a sarin gas attack on Ghouta, a suburb near Damascus, killing more than 1,400 civilians, including hundreds of children.

Under threat of U.S. retaliation, Mr. al-Assad agreed to a Russian-American deal to eliminate his country’s chemical weapons program — which until that time he had denied having — and to join an international treaty banning chemical weapons.

The Organization for the Prohibition of Chemical Weapons, an international monitoring body, was given the task of destroying Syria’s chemical weapon stockpiles in 2013, an undertaking that helped it earn that year’s Nobel Peace Prize.

Over the next nine months, the OPCW dismantled and destroyed some 1,100 metric tons of sarin, VX and mustard gas agents and their delivery mechanisms, and certified, in June 2014, that all of Syria’s declared weapons had been removed.

Why are people worried?

The key word in the OPCW certification of the destruction of Syria’s chemical weapons was that they were the weapons that had originally been “declared” by Syria as part of its arsenal. But Syria’s inventory was not complete.

Even at the time, U.S. and OPCW officials suspected that Mr. al-Assad had concealed some of his stockpiles and chemical weapons facilities from the inspectors, a suspicion borne out three years later, when more than 80 civilians were killed in a chemical bombing by Syrian forces in Khan Sheikhoun.

“We always knew we had not gotten everything, that the Syrians had not been fully forthcoming in their declaration,” Antony J. Blinken, deputy secretary of state under President Obama, told The New York Times at the time.

Almost exactly a year after the Khan Sheikhoun attack, nearly 50 more people were killed on April 7, 2018, in another chemical agent attack near Damascus.

The United States, Britain and France responded by bombing three government-run chemical weapons storage and research facilities near Damascus. But U.S. Defense Department officials acknowledged that the Syrian government had most likely retained some of its ability to use chemical weapons.

How many chemical weapons are left, and where are they now?

As recently as last week, U.S. intelligence agencies were closely monitoring suspected chemical weapons storage sites in Syria, looking for indications that government forces may have been preparing to use remaining stockpiles to prevent rebels from seizing the capital. Now that the Assad government has fallen, there is concern that the weapons could be stolen or used.

On Dec. 9, Israel confirmed that it had carried out airstrikes on suspected chemical weapons and missile stockpiles in Syria to stop the weapons from falling “into the hands of extremists,” said Israel’s foreign minister, Gideon Saar.

Ralf Trapp, an independent consultant on chemical and bioweapons disarmament who has closely followed the fate of Syria’s chemical weapons program and its dismantlement, said that he suspects what remains of the government’s chemical weapons arsenal is small, given Mr. al-Assad’s limited deployment of chemical weapons and the few times he has used them after 2014.

“You did not see massive rocket attacks with sarin gas” he said of the 2017 and 2018 incidents. “We are talking about a small number of grenades. So I would not be surprised if it’s a fairly limited amount that we are talking about.”

How easily could chemical weapons be used?

Not easily. Chemical weapons are not stored in a ready-to-use format. The precursor chemicals for sarin gas are volatile and can only be combined in the warhead just before deployment — hours, or at a maximum, days, Mr. Trapp said.

“Unless they know what the recipe is, how to mix them together and how to do that safely without killing themselves, I would be skeptical about an armed group running into that kind of a stockpile and then actually being able to convert it into an effective weapon,” he added.

What can be done to keep the arsenal safe?

The OPCW announced on Monday that it has been closely monitoring recent developments in Syria as well as the security and integrity of all the country’s declared chemical weapons research, development, production, storage and testing sites. Once a new government is in place, Mr. Trapp said the OPCW will try to work with the new leadership to destroy what remains.

Adam Entous contributed reporting.