A rebel commander said a fall in Iran-backed manpower created an opening this week's assault. Iran's ally Hezbollah has suffered big losses to Israel.

Rebels led by the Islamist militant group Hayat Tahrir al-Sham launched an incursion on Wednesday into a dozen towns and villages in the northwestern province of Aleppo, which is controlled by Syrian President Bashar al-Assad's government. On Friday they made significant inroads into Syria's second city, including reaching the central square.

It was a good fit for Idlib, which had been a source of militant resistance to the Assad government at the very outset of the civil war. As of this writing, HTS fighters have reached the center of Aleppo and seized a town that commands the M5 highway,