Russian President Vladimir Putin addresses servicemen as he visits the Hmeymim air base in Latakia Province, Syria December 11, 2017. Mikhail Klimentyev / Sputnik Photo Agency / Reuters

There are still many unanswered questions about the reported incident with the Iranian drone in northern Israel last week, but two things should be clear. First, the 12-year-old lull between Israel and Hezbollah will come to an end if a new understanding about the rules governing conflict in this region is not reached. And second, Russia will need to help broker that new understanding.

As for the incident itself: Israel claimed that it shot down an Iranian reverse-engineered Lockheed Martin RQ-170 Sentinel drone as it entered the country’s airspace from Jordan on February 10. The RQ-170 is a surveillance drone the size of a small airplane, with a wingspan of over 65 feet. Iran claimed to have downed one in 2011—a fact that the United States has acknowledged—and then used it to build one of its own. According to Israel, this RQ-170 was launched and operated from an Iranian base near the Syrian city of Palmyra. Israeli planes retaliated, targeting both the launch site and various other Iranian and Syrian regime assets in Syria. Iran has denied any role, and Jordan has yet to make a public statement about the apparent violation of its airspace.

The story may well be true. But in the absence of further information, including forensic evidence from the wreckage, one must wonder what would compel Iran to make such an incursion at a time when some in the country are trying to persuade the European signatories of the 2015 nuclear deal to stand by its side and not cave to the Trump administration’s attempt to torpedo it. This would seem an inopportune moment for provocation.

Regardless of the facts, the subsequent events show the risks of a larger confrontation on the Israel-Syria border. The most recent war in the region occurred in 2006, when a local incident involving two captured Israeli soldiers and three killed by Hezbollah escalated into a full-scale Israeli air assault on southern Lebanon and beyond, with retaliation by Hezbollah on Israel. Since then, the border has been relatively calm, with the two sides observing a mutual deterrence.

The civil war in Syria, and Hezbollah’s entry into it in 2012, changed this dynamic. But the real threat of renewed confrontation is of a more recent vintage. It stems from the apparent success of the combined military efforts of Russia, Iran, and Hezbollah to preserve Bashar al-Assad’s rule and help him regain the territory he has lost during Syria’s civil war. This means the possible arrival of even more Hezbollah fighters, supported by Iranian Revolutionary Guard advisers, at the armistice line separating Syria from the Israeli-occupied Syrian Golan Heights. Iran’s military presence on the border, Israel has said, is a red line.

Israel has additional red lines, mainly regarding what Iran does in Syria. It suspects that Assad seeks to establish permanent bases and a port on the Mediterranean, provide its ally Hezbollah with the ability to home-manufacture precision missiles, and carve out a land corridor to supplement its air-supply channel to Hezbollah via Damascus.

Iran and Hezbollah, no doubt, have their own red lines. One of these is likely if Israel carries out airstrikes against their arms convoys and Assad’s forces. Until this past weekend, it was unclear whether Iran and Hezbollah were in a position to enforce such redlines. The answer may now be yes.

This means that the standoff between the two sides is entering a dangerous phase. Neither appears to desire war—at least not now. But both are probing each other’s defenses and tolerance for provocation through a series of tit-for-tat attacks that, in sum, constitute an effort to renegotiate the post-2006 rules of game. Without clear rules, things are almost certain to spin out of control.

Enter Russia. Moscow may be reluctant to assume a political role it has shown little capacity for playing. But as the dominant power in Syria that controls the skies, it has no choice. Unlike any other actor, moreover, it enjoys good relations with all the main actors: Israel, Iran, Hezbollah, and the Syrian regime. There is no reasonable alternative to Russia as balancing power and mediator.

The basis for Russia taking on this responsibility has already been established. It has not blocked Israel from carrying out airstrikes in Syria and—if the drone incident occurred in the way that Israel has claimed—it has allowed Iran to enter Israeli airspace. Has Moscow set limits to what either side can do? Does it understand the rules of the game? Or is this just a good deal of ad-hoc-ism?

Russian leaders will need to reckon with the reality that a major confrontation could occur on their watch in Syria, possibly triggering a larger conflict in the Middle East. It’s doubtful that this would be in their interest. Regardless of the latest incident’s precise nature, therefore, it is a wakeup call for Moscow to restore the mutual deterrence that, while not bringing a lasting peace, at least has kept things stable on Israel’s northern border for 12 years.

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