One by one, the cities around this Iraqi town have fallen. Fallujah. Ramadi. The walled community of Hit.

Islamic State fighters have slaughtered thousands of people as they have tightened their grip on Iraq’s western province of Anbar. But Haditha has remained an outpost of resistance.

Its local tribes and the beleaguered Iraqi army have fought doggedly in the face of persistent attacks. Perhaps even more important, the U.S.-led coalition and the Iraqi government have been determined to prevent its large hydroelectric dam from falling to the insurgents. […]