The US administration’s planned complete withdrawal from Syria is bad news for Israel both militarily and diplomatically, experts said Wednesday, since it will be leaving a vacuum in the war-torn country that will very likely be filled by Iran.

While the US military had only some 2,000 troops in Syria, mostly in the eastern part of the country, and did not actively participate in Israel’s ongoing efforts to prevent the Islamic Republic from entrenching itself there, Iran, and its Russian allies, will likely interpret the American move as an admission of defeat and feel emboldened to act in Syria as they please.

“Until now, while physically present in Syria, the American contribution to Israel’s major struggle — to halt the Iranian war machine in Syria — was marginal to zero,” Maj.-Gen. (res.) Yaakov Amidror, Prime Minister Benjamin Netanyahu’s former national security adviser, told the Los Angeles Times on Wednesday, soon after the shock US withdrawal was announced.

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“The effect of this decision is primarily psychological and diplomatic: With this withdrawal, the US abandons Syria and leaves Israel alone. In those arenas, this is a very significant decision,” he said.

Beyond perceptions, though, the pullout represents a concrete danger for Israel in southeastern Syria, where US troops had played a role in keeping the border region with Iraq from becoming an arms smuggling free-for-all, said Brig. Gen. (res.) Yossi Kuperwasser, a former director of Israel’s Strategic Affairs Ministry and ex-head of the Research Division of Military Intelligence.

The US leaving “would mean that the Assad forces and the Iranians will have full control over Syria, and this would mean that they may try to deliver weapons from Iran through Iraq to Syria and then to Lebanon. And there’s not going to be anything in between to stop them,” he said.

“Especially the Iranians are going to be empowered and feel much stronger,” he added.

Kupperwasser largely backed US President Donald Trump’s claim that the Islamic State’s “territorial caliphate” in Syria had been defeated, but warned that it is “not totally clear that the Islamic State cannot re-emerge, taking advantage of the weakening of their adversaries in this area.”

Trump said the only reason to have troops in Syria was to defeat the Islamic State, an assertion that marked a break with his advisers, notably his top security aide John Bolton, who had said thwarting Iranian entrenchment was also an important US goal in the country.

For Israel, though, thwarting Iran’s ceaseless efforts to entrench itself military in Syria was and continues to be the most pressing foreign policy objective.

Israel has risked all-out war with the Islamic Republic and endured a serious crisis with Russia as it has tackled Iranian assets in Syria, but has seemingly not wavered in its stated commitment to prevent Tehran from establishing a foothold near its borders.

The withdrawal of American troops won’t erase Israel’s gains in keeping Iran on its heels and away from the Golan Heights, but once the last US soldier waves goodbye, a newly emboldened Iran can be expected to make another push to establish military bases near the Israeli border.

All this couldn’t come at a worse time for Israel. Russia, which has promised to keep the Iranians about 100 kilometers away from the border, and which is already regarded as a much bigger player in Syria than the US, is still smarting over on October incident in which one of its spy planes was downed by a Syrian missile during an Israeli strike.

Since then, Israel has apparently scaled back its previously unencumbered air campaign in Syria, and a deconfliction hotline with Moscow has possibly been put on hold.

Russian officials visited Israel Wednesday to see anti-tunnel efforts on the Lebanese border — a visit that Jerusalem reportedly interpreted as a sign of a thaw — but its unclear how Moscow will respond to a renewed Iranian push following the US pullout, and whether it will grant Tehran a freer hand after the US is gone.

Alon Ben David, a senior defense analyst for Israel’s Channel 10 news, called the pullout “a painful hit for Israel,” reflecting Israeli consternation over the move. Channel 10 said Netanyahu had tried hard to persuade Trump to reconsider, and that Jerusalem was deeply disappointed by the withdrawal announcement, which is seen as a victory for Russia, Iran and Hezbollah.

Many conservative policymakers and foreign policy analysts in the United States agreed, calling President Donald Trump’s move “idiotic” and a betrayal of US allies that would only benefit America’s enemies, especially Iran, Hezbollah and Russia.

Withdrawal of the U.S. Special Forces from Syria will strengthen Assad, Putin and Iran. Will weaken our ability to help end the Civil War and protect civilians and refugees. A misguided decision by President Trump. https://t.co/4LeCq9l3Mp — Nicholas Burns (@RNicholasBurns) December 19, 2018

Amateur hour. The decision is not only reckless in its consequences but also in its execution. Most administration officials & military leaders kept in the dark. No proper warning to allies including those who have fought and died. No ability to prepare the battle space. https://t.co/ieDqNYrkgs — Mark Dubowitz (@mdubowitz) December 19, 2018

Trump Administration Syria/Iran policy in one glorious GIF pic.twitter.com/TgTfm7Odjo — Jonathan Schanzer (@JSchanzer) December 19, 2018

“With his decision on Syria, Trump has effectively handed Syria to Russia, Iran, Assad, Hezbollah and Turkey,” tweeted Jonathan Schanzer at the Foundation for Defense of Democracies.

“Obama’s red line debacle was a dark day for American leadership in the Middle East. This is far worse,” he opined.

Officially, Jerusalem said it would deal with the pullout and continue to defend itself. But Netanyahu made little effort to hide his disappointment, with a laconic statement released after the announcement.

“This is, of course, an American decision. We will study its timetable, how it will be implemented and – of course – its implications for us,” the prime minister said, as his domestic political opponents pounded him for a “foreign policy failure.”

Netanyahu said he had this week spoken to Trump and Secretary of State Mike Pompeo, who had stressed that “they have other ways of expressing their influence in the area,” he noted, and vowed to “to maintain the security of Israel and to defend ourselves in this area.”

As guarded as this response may sound — imagine Netanyahu’s fury if Barack Obama had made a similar decision — it cannot cover up the serious disagreement between the Israeli government and the Trump administration. The fact is that Israel wanted to the US to stay, but Trump refused.

According to Hebrew media reports late Wednesday, indeed, Trump flat-out rejected all of Netanyahu’s appeals to reconsider, and simply informed the prime minister that his decision to withdraw all troops from Syria was final.

His administration made Israel happy when it moved the US Embassy to Jerusalem, quit the Iran nuclear deal and imposed the toughest-ever sanctions on Tehran.

Ending the American presence in Syria, leaving Israel alone to deal with Iran, Hezbollah, and Russia, thus marks the first major setback in the hitherto harmonious US-Israel relationship.