SANA / EPA A Syrian army troop patrol in al-Qalamoun Hills, an area in northern rural Damascus, Oct. 13, 2013

Throughout the bloody Syrian conflict, the ruling regime of President Bashar Assad has derided the armed opposition for its reliance on foreign fighters, usually seasoned militants that come from the battlefields of Chechnya, Pakistan, Afghanistan or Iraq. But as a new campaign is set to start in the mountainous corridor between Damascus and the Lebanese border, it is becoming increasingly clear that the government is just as dependent on outsiders for success. In Qalamoun, a strategic region that has been in rebel hands for most of the war, the Iranian-backed Lebanese militia Hizballah is preparing to take on rebels in a drawn-out fight that could dictate the outcome of the Syrian conflict.

The government’s plan to wrest Qalamoun from rebel hands has been long in the planning, an obvious extension of June’s successful campaign to take, with Hizballah’s help, the town of Qusayr, a key rebel stronghold just north of Qalamoun. In regaining Qalamoun, the regime hopes to secure a vital corridor linking Damascus to the coastal province of Latakia, home to the Mediterranean port of Tartous and inhabited by Assad’s Alawite sect. The rebels depend on Qalamoun’s shared border with Lebanon to smuggle in supplies and weapons from supporters in Lebanon. “If the regime takes Qalamoun, it could cause a lot of damage to rebel groups,” says Phillip Smyth, a research fellow at the University of Maryland who specializes in Hizballah and Shi‘ite militias in Syria.

Last week, as Hizballah units prepared for imminent battle in Qalamoun, TIME was able to join some of their forces in a brief foray across the Syrian border from Lebanon to visit a pair of bases in the area’s north. The bases were small — one housed 35 fighters, and the other only 20. But the men were well armed with rocket-propelled grenades, AK-47s, truck-mounted artillery guns and sniper riffles. They all wore the camouflage of Hizballah’s elite special forces. While the immediate area was quiet, the distant thunder of bombs could be heard coming from the village of Mheen, farther to the north, where Syrian government forces battled with the rebels.

“If we don’t defend the Syrian regime, it would fall within two hours,” said Ali, a 27-year-old Lebanese fighter who has served with Hizballah for more than 10 years. He requested that only his first name be used. “Our leadership [in Lebanon] took the decision that it would not be acceptable for Syria to fall [to the Sunni-dominated rebels] because we would be encircled by enemies in Syria and Israel.” (The government arms depot in Mheen has since been captured by the rebels, according to the supreme military commander of the Free Syrian Army, General Salim Idriss, in an interview with Al Arabia TV on Nov. 6.)

Unlike the battle for Qusayr, Qalamoun, with its mountain redoubts, caves and unmapped goat tracks, will not be a set piece battle with clear front lines and decisive victories. Instead it will resemble a guerrilla-type campaign that could continue well into next spring. For that reason, says Smyth, Assad has turned to Hizballah to take the lead. Assad’s military, while still strong, is spread thin. “There is a lot of strain on the soldiers, and the leadership doesn’t trust Sunnis in the ranks not to defect,” says Smyth. Nor can the Syrian army’s new conscripts be expected to do well in such a complex situation. “Hizballah is better equipped. If Assad is going to launch any real offense to secure a strategic zone, he is going to depend on Hizballah.”

And Hizballah is gearing up for Qalamoun with relish. Already the militia has released a slick propaganda video about its preparations for battle, set to a stirring martial beat and full of taunts against the rebels. “After Qusayr it will be Qalamoun,” goes one verse. “You collected the armies of the world and said we will occupy Syria … the heroes are coming and ISIS will be humiliated,” says another, referring to the al-Qaeda-linked Islamic State of Iraq and Syria.

The Syrian army, says Hizballah field commander Abu Jihad, will assist with shelling and air strikes where appropriate, but there is no doubt who is in the lead. “Everything will be under our commandment. The Syrian army will operate according to our plans,” he says, going by his nom de guerre. If true, it represents a striking evolution that reveals the true disarray of Assad’s forces. A Syrian officer in the presidential guard, reached by phone and speaking on condition of anonymity, concurs. “Whenever we are fighting with Hizballah, they take the command and we provide logistics.”

Even with Syrian military support, Abu Jihad anticipates a tough battle. He says there are some 30,000 rebels and rebel supporters in Qalamoun that will have to be defeated, a number backed up by other analysts and Western diplomats in Beirut. But Abu Jihad holds that Hizballah’s forces will be up to the task. The battle has been divided into four fronts, he explains, and Hizballah will take the northern, western and southern fronts along the border with Lebanon while the Syrian forces shore up the highway on the east. Once the rebels are encircled, Hizballah will begin to squeeze. “We will cut everything from them. All sources of life will be cut: water, gas, electricity, heating. Then we will launch our attack.” “We took the decision that none of them is allowed to go out alive,” adds Sheik Ahmad, a high-ranking Hizballah commander in charge of intelligence for Qusayr and Qalamoun.

Residents of Yabroud, a mixed Christian-Muslim town that has long sought to avoid violence, are already bracing for the onslaught. But there is little people can do, says Michael, a Christian resident and spokesman for the antiregime Free Christian movement of Yabroud. He goes by one name and spoke by phone. “We heard that the regime circulated flyers asking people to leave Qalamoun in 24 hours,” he says. But for where? Yabroud is already a refuge for thousands of displaced people fleeing the violence in nearby Homs. “I have no place to go,” laments Michael. “Thousands of people will be killed if the regime attacks.”

Mohammad al-Farouq, a spokesman from Yabroud’s media center, fears that the town will be the next victim of the starvation tactics practiced by the regime in other contested cities. Already, he says, Yabroud’s residents don’t have enough food, fuel and medicine to last the winter. “If this battle starts, it will be a disaster for the civilians.” Given the strategic value of Qalamoun for both sides, and Hizballah’s eagerness to take the lead for Assad, it doesn’t look like there will be much hope for staving off a brutal fight.