It is likely that Israel launched the missile attack in Syria that killed at least 26 pro-government fighters, many of them Iranians, late on Sunday night. The targets included a ground-to-ground missile depot that exploded with the seismic impact of a small earthquake.
Iranian news outlets first confirmed and then denied that Iranian facilities had been destroyed, suggesting that Tehran wants to deny that the incident took place because it does not intend to retaliate against Israel at this time.
Israel has not confirmed officially that it was responsible for the airstrikes, but the Israeli media is reporting them as if there was no doubt that Israel was behind them.
Iran may feel that retaliatory military action against Israel is not in its interests in the days leading up to Donald Trump’s likely withdrawal from the Iran nuclear deal on 12 May.
The Iranian leadership will want to avoid providing Mr Trump with an excuse for his actions, thus enabling them to put as much blame as possible on the US for pulling out of the 2015 agreement.
Israel may calculate that it can expect to benefit from Iranian restraint in Syria for the next few weeks or even months, even if Israel escalates its airstrikes against Iran-related targets.
It is a risky strategy: much depends on the extent of Israeli ambitions in Syria. It can expect strong support from the US and the new, hawkish US Secretary of State Mike Pompeo had just left Israel when the missile attacks took place.
But if the Israeli air war in Syria continues and begins to affect the balance of power in the seven-year civil war, then Iran will certainly retaliate. Iranian reaction to developments affecting its interests in the Middle East – such as the Israeli invasion of Lebanon in 1982 and the US invasion of Iraq in 2003 – have tended in the past to be long delayed but effective.
Sustained Israeli military action in Syria could not single out Iranian targets. It would draw in Russia which does not want to see the military successes of it ally, Bashar al-Assad, reversed by Israel. Relations between Israel and Russia are deteriorating: previously Israel informed the Russians about impending Israeli attacks, but this liaison is reported to have lapsed.
Israeli strikes in Syria have increased this year, primarily focusing on facilities where Iranian fighters and equipped were alleged to be based. Serious incidents include an Israeli warplane shot down returning from a bombing raid in Syria on 9 February and an Israeli attack on the Syrian government’s T4 airbase between Homs and Palmyra on 9 April that killed seven Iranians.
Israel is certainly capable of inflicting losses on Iran in Syria, but would not be able to force them out of the country. Trying to do so might well provoke a wider war. US policy in Syria is contradictory, with Mr Trump demonising Iran as the source of all evil which must be opposed, but also saying that he wants to pull US forces out of the country.
An Israeli-Iranian confrontation in Syria, would add yet another battle front to the conflict there that already has multiple fronts.
If sustained, it could draw in Hezbollah in Lebanon which has been an important ally of Assad. The US may back a more aggressive Israeli posture in Syria, but the single-minded obsession of the Trump administration with Iran as the source of all instability in the Middle East is dangerously simple-minded and injects more instability into a region already deeply unstable.