Syria’s antigovernment forces claimed a stunning advance into Aleppo, in a setback for the government in Damascus and its allies Russia and Iran.

Several armed Syrian opposition groups have taken control of almost all of Aleppo, the second largest city in Syria, according to a war monitoring group and reports from the city. Why it matters: The breach of Aleppo is a dramatic shift in the 13-year Syrian civil war and the rebels' largest offensive since 2020.

The surprise attack, led by the Islamist group Hayat Tahrir al-Sham, was the boldest rebel assault for years in the civil war that has been frozen.