The much-touted attack on Aleppo launched on Oct. 16 has been dovetailed by regime advances in the southern rural areas of Syria. Yet the takeover of the largest Syrian city may prove to be a long and costly battle that President Bashar al-Assad’s regime cannot afford, despite Russian air support. In addition, it may not be the regime’s first priority, as its forces are eyeing supply routes on the city’s southern flank.

Thousands of Shiite militiamen were deployed on Oct. 19 in the Aleppo region under the command of Maj. Gen. Qasem Soleimani, from Iran’s elite Quds Force, in an attempt to recapture Aleppo, as reported by The Washington Post quoting officials from three Iraqi militias. The Iraqi Shiite militia, Kataib Hezbollah, has sent approximately 1,000 fighters from Iraq, who are fighting alongside 2,000 members of the Iranian Islamic Revolutionary Guard Corps.

“The control of Aleppo is essential to President Assad’s national legitimacy. Syria was created after the First World War by the union of the provinces of Aleppo and Damascus. Losing Aleppo would mean for Assad that he is the president of half the country. Strategically, Aleppo is vital to regaining the northwest [the provinces of Idlib and Aleppo] and the control of the Turkish border, directly or via the Kurds,” Syria expert Fabrice Balanche, from the Washington Institute for Near East policy, told Al-Monitor.

The battle for Aleppo has been witnessing ebbs and flows for the last three years. The Syrian army was able to lift the siege of Aleppo in spring 2013 and patiently encircled rebels in the eastern districts. In February 2015, its attempt to cut the last road linking Aleppo to eastern Turkey resulted in failure, with rebels reinforcing their positions, explained Balanche.