The leaflets fell from the sky over Aleppo, offering dire warnings. “If you don’t leave these areas quickly,” they admonished civilians, “you will be annihilated. Save yourselves.… Everyone has left you alone to face your doom.…” As Syrian government forces continue to steamroll through eastern Aleppo, the rebel opposition’s last stronghold in this war-ravaged city, the leaflets aren’t just a warning for residents; they’re also an indication that President Bashar al-Assad is poised for victory. It was only a year ago that the rebels seemed on the verge of taking Aleppo, once Syria’s bustling commercial capital. But due to a...