Mikhail Klimentyev / Kremlin

In the fall of 2015, Russia and Israel held their first talks on “deconfliction,” a disconcerting, vague military arrangement, the aim of which was “preventing misunderstandings” in the Syrian civil war. Russia had just formally entered the conflict, and Israel had already been informally participating through occasional strikes on Hezbollah targets in Syria and some cross-border exchanges of fire. The purpose of deconfliction, it seemed, amounted to a diplomatic version of Ma$e rules: Stay out of my way.

But late last week, something changed. As Israeli jets returned from Syria after bombing a weapons convoy reportedly bound for their foe Hezbollah—allied with Syrian dictator Bashar al-Assad and Iran—Syrian forces fired missiles at them, sparking the most serious incident between the two countries in the six-year war. In a first, the Syrian anti-aircraft missiles triggered Israel’s missile defense system, which intercepted one of the rockets, causing debris to fall over neighboring Jordan. Last Friday, following the incident, an Israeli army official confirmed the Israeli strike on the convoy publicly for the first time.   

Shortly after the episode, Russia took the unusual step of summoning the Israeli ambassador in Moscow to explain what happened. This may have had to do with the Israeli admission or the strike itself; according to one Israeli report, Russian troops were reportedly stationed not far from where the Israeli jets struck in Syria. However, Syria’s unprecedented military response could suggest that the dynamic is shifting, as pro-Assad forces continue to gain ground with Russian and Iranian help and as a new U.S. administration slowly settles in—leaving Israel uncertain of its place in the conflict.

Despite its conflicting priorities, Israel, which wants to keep Iran out of Syria and Hezbollah weak, has managed to keep solid working relations with Russia through the Syrian conflagration. But, as the war progresses, those days may be over. “No matter how good the coordination mechanism between the two sides,” writes Michael Koplow of the Israel Policy Forum, “the fundamental conflict at the heart of Israeli-Russian views on Syria is that Israel’s redline is the establishment of a permanent Iranian presence in Syria and Russia’s redline is the elimination of a permanent Iranian presence in Syria.”

On Sunday, the Syrian ambassador to the UN warned that his government’s response to the Israeli strikes marked a new phase of the conflict, where Israeli attacks would merit further responses. He also claimed that Russia had informed Israel that it no longer had free rein to do what it wishes in Syrian airspace. In a series of tweets on Monday, Daniel Shapiro, the former U.S. ambassador to Israel under President Obama and an Atlantic contributor, suggested that the Israeli-Syrian border may be where Russian President Vladimir Putin decides to test how much leverage he has in the Middle East with President Trump in power.

The Israelis, for their part, vehemently deny that they have been constrained from conducting strikes in Syria. On Sunday, Israeli Defense Minister Avigdor Lieberman vowed to destroy Syria’s air defense system if Israeli jets ever encountered return fire again. On Tuesday, Israeli Prime Minister Benjamin Netanyahu told reporters in Beijing, “It’s simply incorrect to say the Russians are changing their policy toward us.”

Despite Netanyahu’s exhortations, there’s no guarantee that Russia will maintain its tacit agreement with Israel over its activities in Syria, especially as Assad’s prospects only continue to brighten. Should Russia change its mind and tell Israel to cease its activities in Syria, the cost of future Israeli strikes will go up, leaving Bibi with fewer options. He could turn to the U.S. for sympathy—something he may not find within the new administration.

In the meantime, tensions between Israel and Syria continue to escalate. On Sunday, an Israeli drone strike reportedly killed a high-ranking air defense official in the pro-Assad forces. On Monday, Israel confirmed that one of its drones had been shot down in Syria. And, on Wednesday, Syrian opposition outlets reported that Israeli jets had carried out new strikes near Damascus, the fourth such attack in less than a week. Israeli officials declined to comment.