Despite John Kerry’s claim in 2013 to have arranged for the dismantling of Syria’s chemical weapons, Bashar al-Assad’s forces have continued to use them with impunity. Islamic State (IS) has employed chemical weapons as well, as have various anti-regime forces. Hizballah, too, may have already acquired some, and if not, is likely trying to do so. Dany Shoham explains what is at stake:

Although chemical weapons have not brought about a major shift in the course of warfare, they have not been ineffective, offering their users a series of accumulating net benefits, notably intimidating survivors into flight. . . .

It is [also] possible that IS will attempt an act of “mega-sabotage,” meaning a high-impact operation involving chemical weapons or another weapon of mass destruction. The organization is very much inclined to pursue such an operation, either in the Middle East or in Europe or the U.S. Its weakened condition suggests that it is unlikely to pull off such an attack—but its motivation to attempt one is undoubtedly growing.

Of the [groups with chemical weapons], IS is the most troubling. IS has been dented by a variety of adversaries over the past year, but has retained its relatively rudimentary chemical-weapons capacities. . . . The organization has also tried to procure biological and radiological weapons, with no clear outcome as yet. . . .

Beyond the Middle East, the U.S. and Europe are IS’s main targets. . . . Israel, too, has reason to be concerned about IS attempts at chemical attacks. Militants of IS or its affiliates in the Golan Heights have confronted the IDF very little, but there is unverified—though concrete—information in the Israeli media pointing to their possession of chemical weapons.

Hizballah, for its part, could receive chemical or biological weapons from Syria, or, just as likely, from Iran, which is known to have stocks of both.

Early Friday morning, Israel attacked military installations near the Iranian cities of Isfahan and nearby Natanz, the latter being one of the hubs of the country’s nuclear program. Jerusalem is not taking credit for the attack, and none of the details are too certain, but it seems that the attack involved multiple drones, likely launched from within Iran, as well as one or more missiles fired from Syrian or Iraqi airspace. Strikes on Syrian radar systems shortly beforehand probably helped make the attack possible, and there were reportedly strikes on Iraq as well.

Iran itself is downplaying the attack, but the S-300 air-defense batteries in Isfahan appear to have been destroyed or damaged. This is a sophisticated Russian-made system positioned to protect the Natanz nuclear installation. In other words, Israel has demonstrated that Iran’s best technology can’t protect the country’s skies from the IDF. As Yossi Kuperwasser puts it, the attack, combined with the response to the assault on April 13,

clarified to the Iranians that whereas we [Israelis] are not as vulnerable as they thought, they are more vulnerable than they thought. They have difficulty hitting us, but we have no difficulty hitting them.

Nobody knows exactly how the operation was carried out. . . . It is good that a question mark hovers over . . . what exactly Israel did. Let’s keep them wondering. It is good for deniability and good for keeping the enemy uncertain.

The fact that we chose targets that were in the vicinity of a major nuclear facility but were linked to the Iranian missile and air forces was a good message. It communicated that we can reach other targets as well but, as we don’t want escalation, we chose targets nearby that were involved in the attack against Israel. I think it sends the message that if we want to, we can send a stronger message. Israel is not seeking escalation at the moment.