Israel's war planes have been killing Iranians in Syria. There are reasons Iran is not fighting back. These religious wars for Moses and Allah are explained at the Wall Street Journal.

Can Israel’s Clash With Iran Be Contained in Syria?

As the Israel-Iran conflict escalates, Russia comes under pressure to pick sides.

By Yaroslav Trofimov May 3, 2018

DUBAI—The direct military conflict between Israel and Iran has already begun, with a series of increasingly bold (and usually unacknowledged) Israeli strikes on Iranian bases in Syria in recent weeks.

The question now is whether this clash could be contained within Syria—or whether violence could spread to Israeli, Iranian and maybe Lebanese territory, unleashing a regional war.

So far, Israel has been able to act with relative impunity. It enjoys the benefit of a supportive administration in Washington, a Russia that attempts to remain uninvolved—and an Iranian regime that is reluctant to retaliate militarily just as its 2015 nuclear deal with the U.S. and other world powers faces collapse.

But that doesn’t mean that things won’t escalate dramatically in the weeks to come. There is only so much humiliation that Tehran can sustain as it absorbs lethal Israeli strikes, such as Sunday’s bombing near Hama. And it’s only so long that Russia—which has the capacity to shoot down Israeli planes over Syria—can remain on the sidelines.

The timing of this confrontation—triggered by Israel’s decision that it won’t allow the establishment of Iranian military bases and facilities threatening it on Syrian soil—is inconvenient for Tehran.

President Donald Trump faces a May 12 deadline on whether to renew the nuclear deal. Amid Israeli campaigning aiming to prove Iran’s noncompliance with the agreement, Tehran is keen to retain the good will of European states that are crucial for Iran’s economy, and that could prevent a re-imposition of international sanctions.

“The Iranians are wise enough to understand that they are right now being provoked into doing something stupid so that further drastic measures against Iran would be adopted also by the Europeans,” said Adnan Tabatabai, CEO of the Carpo think tank in Germany who has advised the German government on Iranian affairs. “This is why we may continue seeing some strategic patience on the side of the Iranians.”

Iran’s options for responding militarily are risky regardless of what happens with the nuclear deal. The most powerful weapons of Iran’s regional influence are its proxies, most notably Lebanon’s Hezbollah Shiite militia, with its arsenal of sophisticated rockets and missiles. Israel, however, has now made it clear that major attacks by these proxies could prompt it to retaliate against Iran proper.

“Israel has changed. Before, Israel would hit at Iranian proxies. Now, the attitude is: if it’s an Iranian proxy, it’s Iran, and Iran has to pay,” said Meir Javendafar, Iran specialist at IDC Herzliya, an Israeli academic institution and think tank. “If Hezbollah starts firing its hundred thousand missiles at Tel Aviv, you should expect Israel to attack Tehran.”

While neither Iran nor the Syrian regime currently has the means to significantly deter Israeli airstrikes, Russia—with its S-400 air-defense system deployed to Syria—does. Yet, despite years of close military cooperation with Iranian forces and Iranian-backed Shiite militias against Syrian rebels, Russia so far has refused to extend this umbrella against Israeli raids.

“Iran sees Syria as a strategic concern, and as key to creating a deterrent to Israel—while Russia just doesn’t,” said Aniseh Bassiri, Iran specialist at the Royal United Services Institute in London.

While Iranian officials privately seethe about Moscow’s posture, they have shied away from public criticism so far.

“Iran is one of the loneliest countries in the world, strategically,” said Karim Sadjadpour, Iran expert at the Carnegie Endowment for international Peace in Washington. “They have long distrusted Russia, especially because of Putin’s close relations with Israeli leaders, but they don’t have the luxury of a more trustworthy ally in Syria.”

While Russia raised the prospect of delivering the potent S-300 air-defense system to Syria after last month’s U.S., French and British strikes on the Syrian regime’s suspected chemical-weapons facilities, Moscow has since said that no decision on this move has been made. (Russia suspended the delivery of S-300 to Syria in 2010, at Israel’s request—and it may not want the system to be tested in battle, and possibly proven ineffective, by Israel’s air force.)

Russia’s ambassador to Israel, Alexander Shein, highlighted Moscow’s balancing act in an interview with Israel’s Ynet news publication last week. While criticizing Israeli strikes in Syria, Mr. Shein also said Moscow is “concerned” with Iran’s military presence there. “We do understand the reasons Israel feels obligated to carry out such actions in the first place, and it would of course be preferable if they were avoided,” he said.

Write to Yaroslav Trofimov at yaroslav.trofimov@wsj.com

Neither Iran nor the Syrian regime currently has the means to significantly deter Israeli airstrikes; above, missiles and a portrait of Iran’s Supreme Leader Ali Khamenei on display in Tehran last year.