A member of forces loyal to Syrian President Bashar al-Assad in Aleppo. (Omar Sanadiki/Reuters)

Syrian Forces and Pro-Government Militias

Syria’s armed forces and security services (mukhabarat) have long been a vital source of the Assad family’s control of Syria. But after suffering thousands of casualties and desertions, they have come to rely on the support of local irregulars and foreign militiamen, as well as Russian air power, to besiege and bombard opposition-held territory, recapture that territory, and restore control. With their support, Assad’s forces have turned the tide of the war. Since the fall of east Aleppo in December 2016, they control the country’s five most populous cities.

Alawis, members of Assad’s sect, make up much of the army’s top echelons; other minorities are also disproportionately represented among the officer corps. Sunni Arabs, who may comprise nearly two-thirds of the army, are also represented. Conscription is mandatory for all Syrians, and fighting-age Syrian men have been swept up at government checkpoints.

Assad has pledged to restore the state’s authority across all of Syria. But many analysts believe that the state exists in name only across many of the territories ostensibly under its control. Rather, they say, these territories are ruled as fiefs by local warlords. Pro-regime units are often seeking out more parochial interests, whether to earn black-market profits or defend local communities.

What are their capabilities?

The Syrian Arab Army may have as few as twenty-five thousand troops that can be deployed to clear and hold territory. Its overall pre-war strength of some 220,000 active-duty troops has been diminished through casualties of conflict or defections. It has come to rely on militias of regime loyalists that range from groups of neighborhood thugs known as shabeeha (derived from the word “ghost”) to the more professional National Defense Forces, composed of military reservists.

The air force is perhaps the most potent wing of the military, with more than 260 aircraft plus attack helicopters, according to the International Institute for Strategic Studies (IISS), a London-based think tank. The regime has used air power to target not just rebel formations but also populated centers and civilian institutions protected under international law, including hospitals, often with crude barrel bombs.

Such air strikes, along with chemical weapons attacks, have drawn investigations into violations of international humanitarian law. Though the regime gave up some of its most lethal chemical weapons in 2013 amid threats of U.S. intervention, allegations of chlorine attacks persisted, and a sarin attack attributed to the regime in April 2017 prompted U.S. reprisal.

Who are they fighting?

The Syrian army and its allied militias are primarily fighting the Sunni-majority opposition, particularly to consolidate its control of the country’s main population and economic centers along its western spine. They mostly withdrew from Kurdish-majority areas in the north in 2011, and have largely ceded the country’s sparsely populated desert east to the Islamic State.

Hezbollah

The Lebanese Shia movement was established during the country’s civil war and expanded its support by putting up a guerrilla resistance to Israel in subsequent years. Its involvement in Syria’s civil war, though, has implicated the group in Assad’s killing of civilians and political repression, eroding its popularity in the Arab world. In Syria, it has galvanized a mostly Sunni opposition that now sees Hezbollah as a sectarian partisan and a beachhead of Iranian domination of the country.

Syria is a “lifeline” for Hezbollah, providing a pipeline for arms from Iran to Lebanon as well as areas to train. A hostile, Sunni-led successor regime could shut down that support; just as worrisome would be an anarchic Syria in which Sunni extremist groups could thrive. Thus, Hezbollah, at first in secret, answered Iran’s call in 2011 to put down the initial Syrian revolt. It claims to be a bulwark against Sunni extremist movements on the rise in Syria.

Though Hezbollah and Russian forces are tactical allies, efforts at a political settlement will expose differences between them, analysts say. Opposition forces will likely insist on Hezbollah leaving the country if Russia succeeds in brokering peace talks.

What are its capabilities?

Hezbollah has sent military advisors, and eventually, its elite forces and ground troops to fight in Syria. Its forces in Syria numbered between four thousand and eight thousand at the start of 2016, says IISS, and, with Syria’s infantry weakened, they have been vital to rolling back opposition forces and holding territory cleared by Russian air strikes. It has besieged pro-opposition towns such as Madaya and Zabadani, northwest of Damascus near the Lebanese border, and oversaw their evacuations in what some analysts viewed as a project of demographic engineering to install Shia majorities in strategic areas.

Like its Syrian and Iranian allies, it has suffered from heavy battlefield losses, and estimates of fatalities range upwards from a thousand. Its chief military commander in Damascus was killed in May 2016 amid murky circumstances.

The group’s arms convoys have reportedly attracted Israeli air strikes. (Israel, which maintains it is neutral, has not confirmed them.)

Who is it fighting?

Hezbollah militants have primarily fought Sunni opposition forces, particularly along the southwestern border Syria shares with Lebanon. They were decisive in the 2013 battle for al-Qusayr, in which the opposition threatened to cut off a vital regime route between Damascus and the coast, as well as that year’s recapture of the Qalamoun mountains and town of Zabadani on the Syria-Lebanon border from rebel groups.

CFR's timeline of the civil war looks at how the conflict has evolved over nearly six years.

Foreign Shia Militias

Iranian military advisors and Hezbollah militants have been reinforced by other Shia militants, primarily from Afghanistan, Iraq, and Pakistan. Some of the Iraqi militias are offshoots of the Popular Mobilization Fronts fighting to retake Iraqi territory captured by the Islamic State. The Afghan fighters are largely refugees who have long resided in Iran and were recruited by Iran’s Revolutionary Guard Corps with offers of citizenship or payoffs.

Their original aim was to defend Shia holy sites that they believe would be wiped out if Sunni militants toppled Assad’s government. Foremost among them is the tomb of Sayyida Zainab, the prophet Mohammed’s granddaughter, in a southern Damascus suburb. But as pro-Assad Syrian forces have been depleted by defections and casualties, these foreigners have come to a broader defense of the Assad regime, ranging across Syria’s frontlines against opposition groups.

What are their capabilities?

Their ranks have been estimated to be as high as twenty-five thousand. They have proven vital to the regime’s ground fighting, particularly in the battle for Aleppo.

Who are they fighting?

They have primarily clashed with Sunni-led opposition forces, particularly over the contested, populous western spine of the country. Among their battlefield foes are U.S.-backed opposition groups.

Iran

Syria is Iran’s main ally in the Arab world, and Tehran entered the conflict fearing that any successor to the Assad regime led by the country’s Sunni majority would align with its rival Saudi Arabia. As the civil war has dragged on, its fears have shifted to the threat of anarchy in Syria, which would foster conditions in which Sunni jihadi groups could thrive. It has focused most of its efforts in the country’s west, where opposition groups most directly threatened the regime.

In addition, Iran maintains its access to Hezbollah through Syria. It relies on Hezbollah as an asymmetrical deterrent to a militarily dominant Israel, and Syria offers a conduit to arm the Lebanese group. It is also pressing its strategy through demographic engineering, some observers say, including deals in which besieged pro-opposition populations have been evacuated to the northwestern province of Idlib, allowing pro-regime forces to take over strategically valuable areas and Shia majorities to settle there.

What are its capabilities?

Iran has helped keep the Assad regime economically afloat even while it was bearing the weight of international sanctions for its nuclear program. Early on it dispatched military advisors, and later, members of its elite Quds Force and Revolutionary Guard soldiers, their first major deployment abroad. They numbered up to two thousand at the start of 2016, according to IISS. Like Hezbollah, Iran had concealed the depth of its military involvement until mounting funerals made it apparent to the public. It is reported to have suffered several hundred casualties.

Russia

Moscow’s ties to Syria long predate the civil war, and it provided the Assad regime with a diplomatic shield at the United Nations after the start of the uprising. Then, in December 2015, it intervened militarily, focusing on supporting Assad’s campaign in the west and north, particularly in its bid to recapture rebel-held eastern Aleppo. Though Russia claimed to primarily be fighting the Islamic State, analysts said most of its operations have concentrated on other antigovernment groups and civilian targets in opposition-held population centers. The last rebel-held neighborhoods of Aleppo fell in December 2016 after a prolonged siege and intense bombardment. With the opposition weakened, Russia launched a diplomatic process in Astana, the Kazakh capital, that sought to instate a nationwide cease-fire as the groundwork for an eventual political settlement.

Russia’s interests include protecting its military bases on the Mediterranean coast. A deep-water port at Tartus offers Russian naval ships and nuclear submarines their only access to the eastern Mediterranean that does not require transiting the Bosporus, which is controlled by Turkey, a NATO member.

Russia wants to see the regime’s structure remain intact, and its officials cite the anarchy and civil war that followed NATO-led regime changes in Libya as reason to caution against Western support for antigovernment forces in Syria.

What are its capabilities?

Russia has deployed fighter jets and attack helicopters in population centers, providing government-aligned ground forces close air support to retake territory.

Activists and monitoring groups have accused Russia of bombarding such population centers as east Aleppo as part of a scorched-earth strategy meant to deplete rebels and encourage civilians to evacuate or capitulate. Allegations include the use of bunker-buster bombs, which wreak particular destruction on shelters and medical facilities built underground to withstand bombardment. France and the United Kingdom have accused it of war crimes; Moscow has denied targeting civilians.