In September, a Syrian chemical-weapons plant was destroyed, most likely by Israeli airplanes, not far from a high-tech Russian anti-aircraft installation. Yet Russian troops did not respond to—or attempt to prevent—this attack on their Syrian ally. Nor has Moscow acted to protect its coalition partners from numerous other Israeli airstrikes over the past few years. Likewise, Russia did not retaliate when the U.S. launched cruise missiles at a Syrian air-force base in April. Guy Plopsky concludes that, despite repeated threats, the Kremlin wishes to avoid conflict with either America or Israel:

Moscow’s warnings to Israel are . . . directed more toward the Syrian and Russian public than they are toward Jerusalem. Offering no threatening response to Israeli airstrikes would make the Kremlin appear weak, prompting pro-Assad factions to question Moscow’s commitment to the regime and weakening Russia’s influence.

At the same time, Russia has been rebuilding Syria’s air defenses in the hope that they would deter both Israel and the coalition from further strikes. Russia’s defense ministry has mentioned Syrian air defenses in warnings directed at coalition forces and has pledged to “increase [their] effectiveness.” . . .

As for Russia’s own air defenses, Moscow has not utilized them to defend Assad’s forces and is unlikely to do so for fear of an armed confrontation with the U.S. and its partners. Indeed, while Syrian fighters are known to have flown escort missions for Russian strike aircraft, the reverse has not occurred. Furthermore, like Israel, the U.S. maintains a de-confliction line with Russia and has developed agreements to avoid clashes. . . .

Contrary to Kremlin rhetoric, targeting stealth aircraft and cruise missiles remains a major challenge for Russian air defenses. Furthermore, due to the radar horizon limit, even non-stealth aircraft can significantly reduce detection by flying at very low altitudes. Also, sophisticated electronic-warfare systems can degrade the performance of enemy radar. Hence, at long ranges, [even the best Russian surface-to-air missiles] can realistically be expected to intercept only cumbersome targets successfully. . . .

This does not mean Russia’s air defenses in Syria should be neglected. On the contrary: Jerusalem and Washington must keep a close watch, particularly as the post-Islamic State stage of the Syrian conflict sets in.

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.