American commanders have been hailing the advance of the retrained Iraqi Security Forces (ISF) on Ramadi, the key city where they were easily routed some 18 months ago by marauding fighters of the Islamic State militant group (ISIS).

But what they aren’t saying—and are loath to concede, according to well-informed military sources in Washington—is that the security forces of the Iran-backed regime in Baghdad largely consist of Shiite fighters in league with murderous militias that have slaughtered innocent Sunnis after ousting ISIS militants from Tikrit and other battlegrounds in the past year. Ramadi is the capital of the Sunni-dominated Anbar province, and the Shiites are ready to pounce.