FROM a rocky outcrop overlooking a limestone quarry in the desolate valley below, a fighter from Hizbullah surveys what just days before had been territory controlled by militants linked to al-Qaeda. “There were snipers behind every rock,” recalls the young man with a wispy moustache. The operation to drive the jihadists from their mountain lair on Lebanon’s north-east border with Syria began on July 21st. It took only a week for Hizbullah to defeat its militant rivals, adding yet another victory to its growing list of military achievements since war broke out in Syria six years ago.

Along with Russian air power and Iranian military aid, Hizbullah’s ground units have kept the regime of Bashar al-Assad, Syria’s blood-soaked president, in power. The cost has been high. About 2,000 of the group’s fighters, out of a total of perhaps 15,000 (excluding reservists), have died on Syria’s front lines. But the conflict has also transformed Hizbullah, a Lebanese militia-cum-political party. Hardened by the fighting and flush with arms from Iran, it now more closely resembles a regular—and quite effective—army. That worries Israel, its traditional adversary.

Hizbullah’s roots date back to the early 1980s, when Iran’s Revolutionary Guard trained Shia militants to harass the Israeli soldiers then occupying southern Lebanon. The group honed its guerrilla tactics, including car bombs and assassinations, during Lebanon’s civil war. It claimed victory when Israeli forces withdrew from the south in 2000 and fought them to a bloody stalemate again six years later. But during its campaign in Syria Hizbullah has adopted more conventional tactics, and gained a bigger arsenal. It has used tanks, guided missiles and a fleet of drones and fought across deserts, mountains and cities.

Israeli officials report, with some alarm, that Hizbullah has 17 times more rockets than it did a decade ago. The weapons are also more sophisticated, and are said to include anti-aircraft missiles. Hassan Nasrallah, Hizbullah’s leader, says his rockets can now reach anywhere in Israel, including its nuclear reactor in the south and a chemical plant in the north. Israeli war planners are taking the boast seriously. So far Israel has confined its response to actions inside Syria, where it has occasionally bombed weapons caches and Iranian arms convoys bound for Hizbullah. But Israeli officials say Iran is now building missile factories inside Lebanon. That could provoke Israeli strikes within the country. Iranian efforts to build up Hizbullah and other proxy forces on the Syrian side of the Golan Heights—thus opening up a second front against Israel—may also trigger a tougher Israeli response that could spark another conflict. Both sides have reason to fear that the next war may be even worse than the last. Israel argues that the line between the Lebanese state and Hizbullah has blurred in recent years. So if the group launches attacks, Israel should send the entire country “back to the Middle Ages”, says Naftali Bennett, the education minister. Factories, power plants and other major infrastructure are legitimate targets, he says. Mr Nasrallah says he will muster “hundreds of thousands” of volunteers from across the Arab world to fight Israel. A miscalculation by either side could prove devastating.

New friends, with benefits

Hizbullah’s pan-Arab appeal has been damaged by its role in Syria’s sectarian-hued conflict. But it is growing stronger in Lebanon, where it has built new alliances. The group, which is Shia, has stoked Christian fears of Sunni refugees from Syria, who now make up around a quarter of Lebanon’s population. Michel Aoun, the Christian president, has allied himself with Hizbullah’s political wing. Mr Aoun says Hizbullah has a right to keep its weapons to protect Lebanon from Israel, infuriating politicians who want to disarm it. The cabinet is stacked with Hizbullah allies who support the regime in Syria and want it to take back the refugees.

This new political landscape is nowhere more apparent than in the Lebanese border village of Ras Baalbek. Jihadists from Syria infiltrated the Christian enclave in 2014. The local economy suffered as the limestone quarries and hunting lodges closed and the orchards withered. Hizbullah seized the opportunity, sending weapons, night-vision goggles and advisers to help the Christians form a militia to keep the jihadists at bay.

“Israel caricatures Hizbullah as a terrorist organisation,” says Rifaat Nasrallah, the Christian militia’s leader (and no relation of Hassan). “But the resistance is not some external force that comes to terrorise us. They are part of our society. They attend our weddings and funerals. They take care of me and I take care of them.” Alliances forged in the furnace of Syria’s war may be hard to break.