As the Syrian civil war grinds on, Israel now faces two intertwined mortal enemies gaining strength close to its borders—Iran and Hezbollah. And within this context, on Thursday, Syria accused Israel of conducting a strike within its borders, at a facility other observers believe has produced chemical weapons. The strike, which Israel per its policy has not commented on, wouldn’t be Israel’s first, but it’s the first since the U.S. and Russia agreed in July to a cease-fire deal to end the fighting in Syria. That deal was concluded without Israel’s input—but the new strike shows how Israel could continue to shape the battlefield on its own.

The Syrian military said Israeli warplanes fired missiles from Lebanese airspace at a Syrian military positions near Masyaf, killing two army personnel and damaging the site. The Syrian Observatory of Human Rights, a London-based monitoring group that Western news organizations regard as a reliable source of information on the Syrian civil war, said the facility that was struck belonged to Syria’s Scientific Studies and Research Center (SSRC), the country’s premier research institution, and stored surface-to-surface missiles. Western intelligence officials have long believed the SSRC facility in Masyaf, among others, produced chemical weapons. Israeli officials maintained their policy of declining to comment on operational matters, but Amos Yadlin, the former head of Israel’s military intelligence, while not confirming that Israel was responsible, said on Twitter the strike was “not routine.”

“It targeted a Syrian military-scientific center for the development and manufacture of, among other things, precision missiles which will have a significant role in the next round of conflict,” he said. Yadlin also pointed out the factory in Masyaf “produces the chemical weapons and barrel bombs that have killed thousands of Syrian civilians.”

But the reported Israeli strike isn’t unprecedented. Last month Major General Amir Eshel, the outgoing commander of the Israel Air Force, told the Israeli newspaper Haaretz that Israeli jets had hit convoys supplying Hezbollah nearly 100 times over the past five years. The Shia militant group from Lebanon is supported by Iran, and its fighters are battling on Assad’s side in the Syrian civil war.

Israel finds itself in a precarious position as the Syrian civil war grinds on: The United States, its main global ally, has struck a deal with Russia, Syria’s main benefactor, on a cease-fire that is mostly holding; Syrian President Bashar al-Assad is now more in control of his country than at any point since the civil war began more than five years ago; and Iran, which Israel views as an existential threat, and Hezbollah, which it battled for years in Lebanon, have emerged even stronger than they were before the conflict began.

Thursday’s strike, while signaling to its adversaries that Israel will not sit by as forces inimical to it gain strength, also sends a message to the Trump administration that any political resolution of the Syrian conflict must take into account Israel’s long-term security interests. Israel has diplomatic relations with only two of its immediate neighbors, Egypt and Jordan. While it has an unacknowledged relationship with Saudi Arabia, arguably the most important Arab nation, forged on their mutual antipathy toward Iran, Israel views its immediate neighbors as strategic problems. It occupied parts of Lebanon for 22 years until 2000, first to fight Palestinian militants and then to battle Hezbollah; and Syria, where the Assad regime has increased its reliance on Tehran.

Israel has not hidden its concerns about the U.S.-Russia deal on July’s draft agreement for a cease-fire in Syria. Prime Minister Benjamin Netanyahu told Russian President Vladimir Putin that for peace to take hold in Syria, Iran and Hezbollah must withdraw from the country, adding Israel might act unilaterally to protect its interests. Last month Netanyahu told UN Secretary General Antonio Guterres, who was visiting the country, that Iran was building facilities in both Syria and Lebanon to make precision-guided missiles.

Israel views Hezbollah as such a formidable threat it recently concluded a 10-day drill to simulate war with the Shia militant group in the event of multiple infiltrations. Haaretz called it the largest such drill in decades.

Thursday’s strike came a day after the United Nations confirmed that the Assad regime used chemical weapons against civilians in Khan Sheikhoun in April. That’s the attack that prompted the Trump administration to carry out missile strikes on Syrian military facilities. The report represents a blow to Assad as well as Russia, which rejected overwhelming evidence that Syria was behind the use of sarin gas in the attack.

But while Israel’s reported strike Thursday had logic from its vantage point, it could have one unintended consequence: ISIS, under attack from both U.S.-allied forces as well as Syrian government troops and their foreign allies, is now fighting for its life in Syria—a fact anti-Israel conspiracy theorists are already using to give their own reasons for what motivated Thursday’s strike. Syria’s Army Command, for one, said: “This aggression … affirms the direct support provided by the Israeli entity to the ISIS and other terrorist organizations.”