The Syrian government has retaken territory around the northern city of Aleppo, the military said on Tuesday, after two weeks of rebel infighting that has weakened the insurgency against President Bashar Assad.

The internecine conflict among some within the chaotic plethora of rebel groups will allow Assad to portray himself as the only secular alternative in Syria to a radical Islamist regime when peace talks begin in Switzerland on Jan. 22.

His military advances will give the Syrian government delegation greater leverage at the negotiating table. […]