Assad Expands Control in Syria After U.S. Pullback, Pact With Kurds

ISTANBUL—A quickly forged agreement between Kurdish forces and the Syrian government to confront a Turkish military campaign has reshaped alliances in Syria, transforming an erstwhile partner of the U.S. in the fight against Islamic State into a force more closely aligned with Russia and Iran.

Syrian regime military convoys entered areas that have been outside government control for years on Monday, including numerous towns along the northern border with Turkey and near the city of Raqqa, the former de facto capital of terror...