AMMAN — After having helped the regime of Syrian President Bashar al-Assad regain ground in northern part of the country around Aleppo, and in the west along the Lebanese border, Hezbollah, an invaluable ally, launched an offensive in the south. The Shia organization is at the vanguard of this month's incursion by government forces against the Daraa province, one of the rebellion's strongholds on the border with Jordan. "It's the biggest attack against the region," says former Syrian Air Force Colonel Assad al-Zoabi, who is now exiled in Amman.

The immediate goal of the pro-Assad fighters is to rebuild the security buffer zone southwest of the capital that the opposition managed to break, which would allow them to send weapons as far as the Damascus suburbs. But Hezbollah probably has more foresight than that. It could advance to the edge of the Syrian Golan Heights, to the great displeasure of Israel, which occupies this area.

In a rare fit of frankness, Syrian state television acknowledged that it wasn't just Hezbollah fighters who were taking part in the new offensive — but also Iranian officers. The assailants quickly conquered two villages overlooking the countryside around Damascus. The rebels responded by taking Garfa and Namer, two localities along the Damascus-Amman highway, a crucial route for providing Syrian troops with supplies. More than 100 men have been killed in the fierce fights. The end of the sand storm that hit the region last week could enable the Syrian regime to intensify its airstrikes, making it easier for its ground troops to advance.

Deraa is one of the last strongholds of the non-jihadist opposition, the biggest and the most coherent. Since ISIS and al-Nusra Front (al-Qaeda's Syrian branch) have taken large swaths of northern Syria, and the regime has regained control of the city of Homs, the rebels' only hope of a break lies on the southern front.

Over the last six months, the Free Syrian Army rebel fighters and their Islamist allies have been edging forward, so much so that two-thirds of the Hauran, the region around Daraa, is now under their control, as well as the southern half of the Golan. At the same time, different squads of the Free Syrian Army have regrouped in military alliances, the strongest of which have 10,000 men.

Fighting in the Golan Heights on Jan. 28 — Photo: Li Rui/Xinhua/ZUMA

These groups, whose weapons are supplied by Arab and Western supporters via the Jordanian border, have so far been able to avoid internal fighting, which has plagued many in northern Syria. Al-Nusra fighters are present in the south, though in much smaller numbers than the Free Syrian Army, and don't mingle with their rivals. As for ISIS, its only attempt to establish itself in the south, back in November, was defeated by local rebels, who have vowed to resist the terrorist group's "external threat."

Strange bedfellows

But the government offensive could change that. A defeat or simple retreat of the moderate rebels could lead to ISIS infiltration in the Hauran and help al-Nusra become more established in the region. The Syrian Army has proved in the past, especially in the north, its ability to make its enemies rise up against one another. The presence on the ground of Hezbollah and Iran troops, arch enemies of ISIS, could accelerate the radicalization.

The other uncertainty lies with Israel. Its strategy until now has consisted of using the rebel-controlled territories as a buffer zone to protect its Golan Heights troops from forces it considers more hostile — Hezbollah on the one hand and ISIS on the other. That's why anti-Assad fighters have been treated in Israeli hospitals on a regular basis and why Israel provides them with humanitarian aid, food and blankets.

"There's a sort of gentlemen's agreement between us and Israel," says Nijm Abu al-Majd, a Free Syrian Army troop leader. "When the Israeli army attacked the Hezbollah convoy in mid-January, it was sort of a favor. We'd like them to continue."

Does this tacit and tactical rapprochement include the delivery of weapons, as Damascus has been claiming? There's been room for doubt since a December 2014 UN peacekeeper report saying there had been repeated contacts between the two sides. But there has been no proof of that yet. What's certain is that Israel would most definitely not stand and watch as Hezbollah militiamen settled near its borders. Terrified by the idea that ISIS could set foot on its northern border, Jordan will also be keeping a close eye on how the fighting unfolds.

The Damascus-Daraa-Quneitra triangle is about to become the zone of all dangers.