Syria’s civil war puts Israel in a bind: ‘Devil we know’ or Islamist rebels

Syrian President Bashar al-Assad is allied with Israel’s enemy, Iran. The resurgence of the war threatens to invigorate that relationship, undermining Israel’s effort to weaken Iran’s web of allied countries and militias throughout the region.

The rebel group now challenging Assad’s rule, Hayat Tahrir al-Sham, is a U.S.-designated terrorist organization that Israel sees as dangerous to its interests.

“The best option for Israel now is a mutual weakening of those forces, not a decisive victory of any of them," said Harel Chorev, a senior researcher at Tel Aviv University.

Rebel forces from HTS are holding Aleppo after a lightning offensive to reclaim Syria’s second city late last month, a move that exploited the distraction among Assad’s allies—Iran, Russia and Hezbollah—while they engage in other conflicts.

In recent years, Israel has preferred “the devil we know" in Assad, over instability and insecurity created by the Islamist rebel groups, said Eyal Zisser, who follows Syria at Tel Aviv University.

Indeed, before the rebel offensive, Israel had nurtured hopes that Assad could be lured away from Iran through funding and closer ties to more Western-friendly Gulf states, according to Israeli and Arab officials. The Arab league had readmitted Syria after expelling it from the group for its alliance with Iran and Hezbollah. Assad’s forces were lukewarm in support for Hezbollah in its war with Israel, permitting weapons transfers but not committing troops.

With Assad’s regime now facing its greatest challenge in years, Israel worries that those gains are at risk. The rapid rebel advance has also created fresh instability and threatens to upend the regional order. Also, U.S. officials fear that America, which has roughly 900 troops in eastern Syria, might get dragged deeper into the conflict.

For over a decade, Syria has been a crucible for a great-power contest that has drawn in an array of state actors. On Assad’s side, Iran and Russia, along with Hezbollah, have propped up the regime with weapons and fighters. Turkey supports some Syrian opposition groups, as part of its own fight against Kurdish separatists. The U.S. partners with Kurdish-led militias in Syria’s northeast in a campaign against Islamic State extremists.

Israel took a back seat at the outbreak of the Syrian civil war in 2011, but as Iran’s presence in that conflict deepened, and the war drew in Hezbollah, that stance changed. By 2014, Israel had begun what it termed “the war between the wars" in Syria, mostly focused on disrupting the flow of arms and other illicit supplies to its enemy Hezbollah in Lebanon.

Since fighting between Israel and Hezbollah in Lebanon intensified in recent months, Israel has stepped up the pace of its strikes in Syria, including an audacious special forces raid to destroy an alleged Iranian missile factory producing weapons for Hezbollah.

“We’re constantly monitoring what is happening in Syria," Israeli Prime Minister Benjamin Netanyahu said on Sunday after rebels swept into Aleppo.

In recent years, Assad had attempted to mend ties with Arab states that opposed his alliance with Iran and Hezbollah. The Arab League voted in 2023 to normalize ties with Syria and reinstate it as a member. The decision was contingent on Syria engaging with Arab states to find a political solution to the civil war, something it hasn’t so far done in any meaningful way.

There were signs, too, that the Syrian regime was reluctant to throw its forces behind Hezbollah in its war with Israel in the past year. Assad didn’t send the group military aid or troops, and his forces refrained from retaliating for the killing of Hezbollah’s leader Hassan Nasrallah. But the Syrian leader did allow the flow of Iranian weapons to Hezbollah to continue through his country’s borders.

Israel in the past funded the Free Syrian Army opposition forces as they took territory close to its border. It also offered medical treatment in its hospitals to injured fighters from the Nusra Front, an Islamist rebel group that was the precursor to HTS.

But that rebel group’s blend of nationalism and Islamism, which echoes the ideology of Afghanistan’s Taliban and Palestinian Hamas, is regarded by Israel as a dangerous threat, particularly were it to come to power in neighboring Syria.

The fighting in Syria also risks Israel’s cease-fire in Lebanon, which is already strained by exchanges of fire between Israel and Hezbollah. Israel’s military has significantly degraded Hezbollah’s leadership and military capabilities in the past months of intensive fighting, but hasn’t uprooted the group. Israeli strikes to prevent Hezbollah rearming risk straying into cease-fire violations.

Netanyahu said that Israel would act to prevent Hezbollah rearmament through Syria’s territory. “We are committed to defending the critical interests of the State of Israel, and also to preserving the war’s achievements," Netanyahu said Sunday.

Israel’s military launched an airstrike on Damascus on Tuesday, saying it was targeting Hezbollah’s representative to the Syrian military.

Dov Lieber, Summer Said and Sune Engel Rasmussen contributed to this article.