Though it has lost substantial territory recently, including almost all of the province of Idlib in the north and the historic city of Palmyra, the regime has held on to strategic military bases including the airport in Deir Ezzor, the T4 base in eastern Homs and the Tha’ala base in the south, near Deraa.

“There was a practical calculation in Palmyra,” said Kheder Khaddour, a Syrian expert with the Carnegie Middle East Center who has studied state institutions and their activities during the war. “There was no real confrontation with Daesh [Isis], and they preferred to withdraw in the face of a powerful offensive as they don’t want to lose army officers.”

Withdrawals likely preserved the lives of hundreds of officers, allowing them to regroup closer to the regime’s western heartland, where it controls major population centres like Hama, Homs, Damascus and Latakia.

In Aleppo, the rebels and their backers fear the total collapse of services in the city and worry about governing the millions of civilians still living in the government-held areas under what is likely to be a vengeful and brutal aerial campaign.