Iraqi forces are on a westward push to retake Anbar, a sprawling Sunni-dominated desert province captured by the Islamic State group in their offensive last year. But as the battles for Tikrit and Ramadi have shown, it will be a hard slog for a much-diminished Iraqi army — especially given Baghdad’s reticence to arm Sunni tribesmen and local fears of the Shiite militias backing government forces.

Earlier this month, Iraqi forces captured the northern Sunni-majority city of Tikrit from the Islamic State group, but only with the backing from Iranian-trained and Iran-funded Shiite militias and U.S. airstrikes — methods that cannot work in Anbar province.

The Islamic State is estimated to hold at least 65 percent of the vast province at this point.

The past weeks of seesaw battles in Anbar, with progress in areas like Garma east of Fallujah, a stalemate in the biggest city of Ramadi and an Iraqi rout near Lake Tharthar, show that the army still needs help. But relying on erstwhile Shiite militia allies may not be palatable to locals. […]