Israel is likely to continue striking Hezbollah targets in Syria but is also “wary” of the rapid advance that the Islamist rebels opposing its regime have made, military analysts have told the JC.

They describe Jerusalem as open to the opportunities created by disruption to Iran’s “Axis of Resistance” as Bashar al-Assad’s forces fall back, but concerned about the threat posed by Sunni extremists.

In the last week, Hayat Tahrir al-Sham (HTS), an Islamist offshoot of Al-Qaeda that has governed a swathe of territory in Syria’s north west for several years, and the Syrian National Army (SNA), which is backed by Turkey, have seized Aleppo and advanced towards the major central city of Hama.

Taking the Assad regime, his Iranian supporters and the international community by surprise, the resurgence of hostilities in Syria has also left Israel’s security establishment concerned.

"From Israel’s perspective, the rebel advance in northern Syria further isolates Iran and Hezbollah, though Israel remains wary of the growing influence of HTS, a Sunni Islamist group that shares ideological ties with Hamas,” said Avi Melamed, a former Israeli intelligence official and Arab affairs adviser to Prime Minister Ehud Olmert. 

"While HTS does not pose a direct threat to Israel at this stage, the possibility remains that its momentum could lead to future challenges.”

After the start of the Syrian Civil War in 2011, Hezbollah and Iran began sending forces to bolster Assad’s regime. Alongside Russian air support, these proved crucial to preventing the Ba’athist government from collapsing.

By deepening their involvement in Syria, however, they also secured the country as a key route to supply arms from Iran to Hezbollah in Lebanon. 

Fighters set alight a picture of Syrian President Bashar al-Assad in front of a building that was seized by jihadists (Photo: Getty Images)

“The Assad regime allowed Syria to be the Philadelphi Corridor [the strip of Gaza bordering Egypt] on steroids,” said Lt. Col. (res.) Marco Moreno, a former senior officer in the IDF’s Human Intelligence Unit 504.

Many of the weapons Hezbollah used against Israel in the recent war were transferred to them via Syria, he claimed.

During Israel’s war against Hamas and Hezbollah, the IDF has struck numerous targets within Syria, including sites on the Lebanese border, to prevent smuggling.

While the advance of HTS and the SNA will disrupt the Shia militia’s ability to resupply itself, Israel is concerned at their growing strength.

"They are not our friends,” said Colonel Miri Eisin, a former Israeli Army intelligence officer who specialised in Syria. “Our enemy's enemy is not our friend.”

In Aleppo, she claimed, the rebels have taken over several “exceedingly important” military sites.

As they advance further south they will approach locations believed to house the Assad regime’s chemical weapons stockpile.

The IDF will be forced to take "preemptive action" against the rebels if they manage to get hold of them, Ha'aretz reported on Tuesday.

"The rebels are very scary to me no matter who the bad guy is who is opposing them,” Eisen said.

In large part, the rapid advance of HTS and the SNA has been enabled by both Israeli strikes against Iranian-backed groups that support the Syrian regime, and Hezbollah being forced to divert resources from Syria into Lebanon to fight Israel.

Speaking to Israel’s Channel 12 on Sunday, one rebel commander said: “We looked at the [Israeli ceasefire] agreement with Hezbollah and understood that this is the time to liberate our lands.

“This operation was critical. We will not let Hezbollah fight in our areas and we will not let the Iranians take root there.”

“The Hezbollah forces in Syria who came back to Lebanon were the commanders. They are those who know how to fight,” Eisen said. 

"This created weakness. We so decimated the Hezbollah leadership in Lebanon I don’t see them now coming to help.”

Moreno said: “The rebels have been waiting with plans for a long time, and once they saw that we weakened and harmed Hezbollah in Lebanon – and in Syria – they took advantage of the opportunity to attack.”

As the fight between Assad and the rebels continues, Israel is likely to continue striking the same Hezbollah targets that previously hit in Syria, Eisen said.

"Israeli airstrikes on Iranian infrastructure in Syria continue to disrupt Iran’s military presence there, straining its relations with Assad, who has refrained from responding to Israeli attacks,” Melamed said. 

"This ongoing Israeli pressure, coupled with the rebel offensive, weakens the ‘Axis of Resistance’ and challenges Iran’s hegemonic ambitions.”

On Tuesday, the IDF took responsibility for an airstrike near Damascus that killed Hezbollah’s liaison with the Syrian army.

Israel claimed that Salman Jumaa’s death was a blow to the Lebanese militia's plans to rearm and entrench themselves in Syria.

Syria’s rebels are currently engaged in fighting around the outskirts of Hama, which lies on the route from Aleppo to Damascus. 

If it falls, the survival of Assad’s government will be at stake – an outcome Israeli intelligence is said to fear.

“The fall of the regime could create chaos, and it’s not clear who would rule there,” Carmit Valensi, head of the Northern Arena Program at the Institute for National Security Studies in Tel Aviv, told The Times of Israel.

“There won’t be an address that Israel likes, whom you can hold a conversation with through military force or other methods.”

Brig. Gen. (res.) Dedy Simhi, former chief of staff of the IDF Home Front Command, said he would prefer Assad weakened and “bleeding in power” rather than Syria completely falling apart. 

"Israel must sit on the sidelines for now, avoid intervention, and be prepared for anything that might happen,” he said.

"A situation in which another country on Israel's border falls into instability is disturbing and worrying,” an Israeli official told Ha’aretz.

"We need to be ready for any possibility, including that the Assad regime falls and terror groups come to pose a new threat to Israel.”