The multisided war in Syria is moving into a critical phase in the province of Aleppo, as rebel groups and foreign powers, such as Iran, Russia and Turkey, try to strike a decisive blow.
In recent weeks, the Syrian regime and its Shiite ally Iran have mobilized thousands of local and foreign Shiite fighters to capture Aleppo from rebels with the help of Russian airstrikes.
“He who controls Aleppo wins the war,” said Elias Farhat, a retired Lebanese general and military strategist based in Beirut.
Before the war, the city of Aleppo was Syria’s most populous urban center and its economic hub. If the regime could seize back full control, it would tighten the government’s grip on the western half of the country, including the coastal region and the capital Damascus.
For more than a month now, Iran has been leading the operation in southern Aleppo province aimed at severing rebel supply lines and completing a siege of opposition-controlled neighborhoods in the city of Aleppo, according to fighters and activists on both sides. Several rebel fighters in southern Aleppo said moderate factions tied to the Western-backed Free Syrian Army, or FSA, as well as Islamists and the Syrian branch of al Qaeda, the Nusra Front, have been rallying and uniting over the past two weeks to confront the Iranian-led campaign with the backing of Turkey and its allies.
“We have divided the area into different zones,” said a member of an FSA-linked group called Jaish al-Nasr who goes by the nom de guerre Lt. Abu al-Majd. “We attack simultaneously to break down the cohesion of regime forces.”
Sunni rebels—who are fighting both the regime and extremist group Islamic State—are trying to hold on to the parts of Aleppo they control as a lifeline through which most of their supplies are ferried. The province is home to the last stretch of border between Syria and Turkey controlled by Islamic State, which the U.S. and its allies are pressing Turkey to deploy a large number of troops along the border to seal it.
Despite mounting pressure on Islamic State, the group has made some modest gains in Aleppo in recent weeks by capturing some areas from both the rebels and regime.
For the Syrian Kurds, who have gained territory and power over the past year as a result of their lead role in fighting Islamic State, Aleppo is a missing link. Parts of the province come between Kurdish strongholds in northeastern Syria and a major Kurdish enclave in the northwest.
More than any other place in Syria, Aleppo reflects the tangled web of local and regional interests that are vying to control Syria’s future. But the battle for the province also clearly illustrates the challenges facing the U.S. and its allies—as well as the regime’s main backers Russia and Iran—as all wade deeper into the conflict.
Analysts see it as an example of the quagmire the U.S. has been eager to avoid since the start of the conflict more than four years ago, and what President Barack Obama warned the Russians from sinking deeper into this week.
“It is a minefield,” Fawaz Gerges, a professor of international relations at the London School of Economics, said of Aleppo. “Multiple players with clashing local, regional and global interests.”
In the wake of last month’s Paris attacks, France, the U.K. and U.S. have said that their priority is crushing Islamic State—not ousting President Bashar al-Assad. But for many of the warring parties and their regional backers, the goal remains the same: Capture territory at the expense of each other.
Mr. Gerges said it is this discord that has allowed Islamic State to thrive and will make the U.S.-led task of defeating it all the more formidable.
“ISIS has been able to exploit these divisions and cleavages,” he said, using another name for the group.
The regime and its Iranian backers touted last month the breaking of a two-year siege imposed by Islamic State on an air base in eastern Aleppo. But the biggest military push in Aleppo by the regime and its allies isn’t against Islamic State. The Sunni extremist group controls areas in the east and north of the province. Iran and Russia have instead focused their firepower on the southern part of the province against a constellation of rebel groups backed by Qatar, Saudi Arabia and Turkey and the Nusra Front.
Many of Mr. Assad’s opponents see Nusra Front as a partner in their war against him and not a terrorist organization, as it is deemed by the U.S. and others.
These people say Iran is so invested in the battle that one of its top military commanders, Maj. Gen. Qasem Soleimani, is leading it. More than 50 Iranian and Iranian-backed Shiite fighters, including senior officers, have been killed just at this front over the past month, according to a tally compiled mainly from funeral notices issued by pro-Iran militiamen and their supporters and posted on social media.
Ahmed al-Ahmed, a spokesman for the rebel group Failaq al-Sham which fights in southern Aleppo, said Gen. Soleimani was wounded last week when a roadside bomb detonated in his path in the village of al-Eiss in the countryside south of Aleppo.
U.S. officials say they are investigating these reports while Iranian military officials denied them, calling them disinformation by Tehran’s opponents.
Gen. Soleimani is commander of overseas operations for Iran’s powerful military unit, the Islamic Revolutionary Guard Corps, or IRGC. He leads Iran’s overall military effort to prop up Mr. Assad with the help of regional proxies such as the Lebanese Shiite militia Hezbollah.
Officially Iran says it only has military advisers embedded with regime forces. But analysts tracking its activities in Syria say it has significantly increased its presence in recent months with a fresh influx of its own fighters as well as Shiite militiamen it oversees from Afghanistan, Iraq, Lebanon and Pakistan.
Last week, rebels succeeded in recapturing several towns and villages but al-Eiss—the place where Gen. Soleimani is said to have been wounded—remains in regime hands, according to opposition activists.
But Russia is keeping up the pressure on rebels in Aleppo. In the aftermath of the downing of one of its jets by Turkey on Nov. 24, Russian warplanes have regularly bombed the area around the town of Azaz—a passageway for convoys from Turkey destined to rebel areas in Aleppo and beyond. It is also a safe haven of sorts for many displaced civilians.
And for the past 10 days, rebels have been embroiled in clashes with Kurdish militias in the northwestern corner of Aleppo around the city of Afreen. Both sides accuse each other of having started the fight and of committing atrocities against civilians in the area. On Thursday, the two sides announced a tentative cease-fire, but it remains to be seen whether it will hold.
Days before, Saleh Muslim, leader of the main Syrian Kurdish political party tied to the militias, said Kurdish fighters in northeast Syria currently working with the U.S. to fight Islamic State would eventually come to the aid of their compatriots in Afreen—one of the self-rule cantons declared by Kurds in northern Syria.
“The area is historically Kurdish and we have an interest in fighting Daesh [Islamic State] and all the other terrorist groups there,” he said.
—Jay Solomon in Washington contributed to this article.
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