BEIRUT — In the neighborhood of Mouawad, the Syrian war never feels very far away. Yet locals see Hezbollah, the Shia political party that has an armed movement in Lebanon, as keeping them safe from the civil war raging across the border — even more so since Hezbollah's recent victories on the battlefield in Syria.

"Our men fight in Aleppo to keep Beirut safe as well," says Hassan al-Haji, a local fruit vendor on the main road of this outlying neighborhood of the Lebanese capital. "The takfiri of ISIS would like to cut all our heads off too."

This is where Hezbollah-controlled Beirut begins, home to its political leadership, which has bet almost everything on victory in Syria. In his latest speech, Hezbollah leader Hassan Nasrallah went so far as to say that his men will remain in Syria "for centuries" if necessary. Other leading figures agree, explaining that they are in Syria because they were "invited by the government, which is legitimate whether you like it or not — unlike the Turks and Saudis, who send thousands of unwanted terrorists."

While muttering insh'Allah — "God willing" — the leaders are optimistic about their prospects. "Turkey cannot send troops because they don't have air cover, unless they shoot down 150 Russian jets," says one. "The Saudis, on the other hand, just don't have the know-how — look at what's happening in Yemen."

Crossing just a few kilometers into southern Beirut from Mouawad, and passing through other Hezbollah-dominated areas such as Bir el-Abed and Bourj el-Barajneh, the urban landscape changes radically. The city's New York-like downtown and the Parisian air of the Monot neighborhood disappear, replaced by Arabic graffiti calling for "decolonization." Posters and altars commemorate countless martyrs, thousands of young men who have lost their lives on the front. Concrete barriers rise in the middle of trafficked streets, forcing cars into tortuous turns to reach or bypass buildings deemed "sensitive locations."

Bedfellows against ISIS

ISIS extremists have indeed targeted this part of Beirut several times in the recent past, killing more than 40 people on the eve of November's attacks in Paris. They claimed vengeance for Hezbollah's role in the Syrian war, where its 2013 offensive saved Syrian President Bashar al-Assad's regime. In fact, the Shia militia is the regime's principal ally on the ground and a bulwark of Iran's strategy to prop up the Syrian government in Damascus.

Hezbollah has been the model for Tehran's projection of force abroad, a tactic that has since been replicated in Iraq, where the Shia, state-sponsored "Popular Mobilization Forces" aid the Iraqi government in fighting ISIS there.

For the first time, these forces are fighting side by side in the increasingly vicious battle for Aleppo, Syria's largest city. "These are just rough estimates, but the anti-Assad rebels are intercepting more and more conversations in Farsi, Kurdish and Iraqi dialects," says Hossam Abouzahr of the Rafik Hariri Center for the Middle East.

Official sources report that there are between 8,000 and 10,000 Hezbollah militants on the ground, supported by 6,000 Iraqi fighters, 3,500 Afghans and 2,000 Pakistanis, all coordinated by between 1,500 and 3,000 Iranian soldiers.

Russia's entry into the conflict late last year turned the tide of the war, with Moscow establishing a war room to coordinate and plan battlefield actions between its forces and those of Assad, Hezbollah and Iran. Russia's stated priority is to capture Aleppo from the rebels. "Liberating the city would return effective control of the country to the government," a Hezbollah official says. "Talk of regime change is a thing of the past."

On the regional front, the alliance seeks to strike a blow to Turkish and Saudi ambitions. The Sunni powers have their own "foreign legion" on the ground, composed of Turkic fighters from Central Asia and other "volunteers" from the Arab world. In the battlefields of Syria's proxy global war, it's mainly irregular foreign fighters who are dying. Soon, though, that could change — and standing armies may join the deepening mire.