The ousting of Islamic State group forces from the Iraqi town of Sinjar is being touted by Kurdish leaders as a major military victory. But commanders on the ground say the extremists largely withdrew, fleeing during a pause in airstrikes.

The capture of Sinjar by U.S.-backed Kurdish fighters last week did mark a significant gain against the extremists, cutting off a main supply route between Islamic State group territories in Iraq and Syria.

The fighters’ apparent escape suggests the Kurds’ priority was to seize the town —both for its strategic and symbolic value — not trap and crush the IS forces in it outright. IS’s tactical retreat also points to the pragmatism that the group can show when badly outgunned — a contrast to other cases when its jihadis fight to the death, usually during offensives when they aim to wreak as much damage as possible before being killed. […]