Analysis by Mick Krever, CNN

(CNN) — Israeli Prime Minister Benjamin Netanyahu on Sunday said that the collapse of Bashar al-Assad’s regime in Syria was a “direct result” of Israel’s military campaign against Iran and its proxy in Lebanon, Hezbollah.

“This is a historic day in the history of the Middle East,” he said.

But in a sign of the potential danger Israel feels from unknown rulers in Damascus, Netanyahu said that he had ordered the military to seize the buffer zone that separates the Israeli-occupied Golan Heights from the rest of Syria.

“Together with the Defense Minister, and with full backing from the Cabinet, I directed the IDF yesterday to take control of the buffer zone and the dominant positions near it,” he said while visiting the Golan Heights. “We will not allow any hostile force to establish itself on our border.”

It is the first time Israeli troops would be stationed in the buffer zone since a 1974 agreement establishing the line of control between Israel and Syria, though they have in the past entered the no-man’s land for brief periods. Since 1974, the buffer zone has been patrolled by United Nations peacekeepers. Israel captured the Golan Heights from Syria in 1967 and annexed it in 1981.

Israeli leaders are watching events across the border in Syria with a mix of trepidation and glee, as 50 years of detente were upended in a matter of hours.

“We don’t know much,” said Boaz Shapira, a researcher with the Alma Foundation, a think tank dedicated to issues in northern Israel. “The situation that we were used to in Syria in the past – 50 years with the Assad regime – has changed completely.”

Bashar al-Assad was hardly an ally, but there was an understanding that allowed the countries to coexist. Though Israel occasionally offered treatment to casualties of Syria’s civil war, it maintained official neutrality in the conflict. The Israeli military has also for years targeted supply lines of Iran and its proxy Hezbollah in Syria – most notably killing Iranian military commanders in the Iranian consulate in Damascus, in April – but avoided targeting the Assad regime itself.

The rebels’ rapid capture of Damascus means that Israeli leaders will have to evaluate the implications for their own security.

Iran has now lost one of its most important bulwarks in the region. That will be cause for celebration in Israel, which has been fighting Iranian-backed forces in Gaza (Hamas) and Lebanon (Hezbollah) since October last year.

Netanyahu, who declared that the assassination of Hezbollah leader Hassan Nasrallah was a step towards changing “the balance of power in the region for years to come,” will see this as advancing that goal.

Mordechai Kedar, who specialized in Syria affairs during a 25-year career in Israeli military intelligence, said that the events in Syria were a domino effect from Hamas’ October 7 attack on Israel. “It’s not only Israel – it’s the whole Middle East will celebrate,” he told CNN.

The collapse of the Assad regime is a “severe blow” for Iran, said Amos Yadlin, a former major general in the Israel Defense Forces, who also served as chief of the Military Intelligence Directorate.

“The rebels tearing down posters of (Iranian commander Qasem) Soleimani and Nasrallah from the Iranian embassy in Damascus illustrate the severity of the blow to the axis,” he said. “Rebuilding Hezbollah seems even more difficult with the loss of Syria, which was a logistical rearguard for weapons from Assad, Iran, and Russia.”

On the other hand, no one quite knows – including in Israel – who the rebels are who now control Syria, and how they will implement their power.

The offensive was led by Hayat Tahrir al-Sham, which was formerly an al Qaeda affiliate. The US Government still has a $10 million bounty on the head of its leader, Abu Mohammad al-Jolani, whose real name is Ahmed al-Sharaa.

Kedar said that despite their radical roots, the opening indications were positive. “So far, they are rather rational,” he said. “For example, they are leaving the government to run the country.”

Jolani has called on rebel forces to leave state institutions unharmed. “To all military forces in the city of Damascus, it is strictly forbidden to approach public institutions, which will remain under the supervision of the former Prime Minister until they are officially handed over, and it is also forbidden to fire bullets into the air,” he wrote on Telegram.

“Here, they are learning from the mistakes of the American in Iraq. They don’t want to destroy the country. They want the system to work – of course under different rules and different leadership. This is a very rational way to run the country.”

Yadlin said that Jolani had “demonstrated great political sophistication and conquered Syria almost without a fight.”

“In the short term, the rebels are not a threat to Israel,” he said. “When he is required to establish his rule in Syria, he will not get involved with the most powerful military force in the region. Israel needs to shape the rules of the game against Syria in the same aggressive manner in which it does so in Lebanon.”

That view is not universal. Israel’s Minister of Diaspora and Combating Antisemitism Amichai Chiklisaid said in a statement that “the bottom line is that most of Syria is now under the control of affiliates of al-Qaeda and Daesh.” He called for the Israeli military to establish full control within the buffer zone that has since 1974 existed between Israeli- and Syrian-controlled territory.

Indeed, Israel’s top priority will be securing its border with Syria. The IDF said the deployment of troops within the Golan buffer zone was made “to ensure the safety of the communities of the Golan Heights and the citizens of Israel.”

Shapira said he doubted Israel would want to provoke the new leaders in Damascus by pushing into Syrian-controlled Golan. “Taking more territory means we have to deal with other players who might not be so happy about it,” he added.

“There are dozens of different militias,” Shapira said. “It’s going to be very challenging for Israel.”

The Israeli military, in its statement about operations in the Golan, said: “The State of Israel does not interfere in in the domestic conflict within Syria.”

Israel’s top security and political leaders have been mostly mum on events in Syria – no doubt, as they evaluate how to react.

Opposition leader Yair Lapid said that Assad’s ouster emphasized the need “to create a strong regional coalition with Saudi Arabia and the Abraham Accords countries (Bahrain, UAE, Morocco, Sudan) in order to jointly address regional instability. The Iranian axis has weakened significantly, and Israel needs to strive for a comprehensive political achievement that will also assist it in Gaza and the West Bank.”

CNN’s Abeer Salman and Mike Schwartz in Jerusalem contributed to this report.