Opinion writer

The capture of Ramadi last weekend by Islamic State fighters is a significant setback for U.S. strategy in Iraq and shows that, nearly a year after the extremists overran Mosul, the United States still doesn’t have a viable plan for protecting the country’s Sunni areas.

The collapse of the Iraqi army in Ramadi, the capital of Anbar province, was in some ways a replay of the Mosul debacle in June 2014. The Shiite-dominated Iraqi military, though trained and retrained by the United States, appeared to lack the leadership or will to fight off a relatively small but ferocious onslaught of Sunni insurgents.

The Ramadi defeat exposed the sectarian tensions that underlie this war. Among the urgent questions: Are Shiite regular army troops ready to fight and die to protect Sunnis, or will their lines collapse in Sunni areas, as happened in Mosul and now Ramadi? If the tougher Iranian-backed Shiite militias are sent instead to do the job, will the Sunni population see them as a Shiite occupation army — setting the stage for a generation of sectarian revenge killing?

U.S. Central Command offered bland reassurances in the hours before the lines buckled in Ramadi. Via teleconference from the Middle East, Marine Brig. Gen. Thomas D. Weidley told reporters Friday that the U.S.-led coalition’s strategy was on track. Ramadi was “contested,” he said, but the Islamic State was “on the defensive” throughout Iraq and Syria, and resistance was mostly “small-scale, localized, harassing attacks.” He said the U.S.-led coalition had conducted 165 airstrikes in the past month to support the Iraqis and that coalition planners were “working closely with the Iraqi security forces to control critical infrastructure.”

The Centcom briefing proved grossly overoptimistic. According to field reports compiled by a consulting firm, the extremists began Friday with a car bomb attack in Albu Diab, north of the city, that was a “likely diversion tactic.” As Iraqi troops rushed north, the insurgents sent a wave of at least four car bombs into the city center. They did their work. The government defense lines broke.

Given that the Islamic State’s drive to capture Ramadi has been predicted for weeks, why didn’t U.S. and Iraqi planners reinforce the garrison there? Why didn’t coalition forces fight harder to control Camp Blue Diamond, a former U.S. military base on the northwest edge of the city? Why didn’t the coalition add troops to protect Ramadi’s provincial version of the Green Zone in the center of the city? Why were Islamic State fighters allowed to capture new stores of Iraqi weapons and liberate scores of their compatriots in Ramadi’s jails — adding new arms and men at a strike?

The Islamic State’s breakthrough in Ramadi brought wild celebration in other Sunni areas under its control. The group released a video Monday that appeared to show jubilant Iraqi men and boys in the Nineveh area spontaneously dancing and waving its black-and-white banners. The exuberant faces in the video, titled “Glad Tidings of the Supporters with the Conquests of the Predators of al-Anbar,” show how success begets success in the Iraqi conflict. Another jihadist video shows newly freed prisoners kissing the ground. Celebrations of the Ramadi victory, with festive, flag-waving crowds, were posted from as far away as Tripoli, Libya.

What’s worse, the Ramadi defeat showed that the cornerstone of U.S. strategy for Iraq — a Sunni tribal force that can work with the Iraqi military to clear and hold areas seized by the Islamic State — isn’t in place yet. The Iraqi parliament still hasn’t passed a long-promised law to create such a force, and arms shipments to Sunni fighters have been delayed or ignored by the Baghdad government.

“If it stays like this, it’s going to lead to a civil war,” warned Sheik Abdul Razak, a leader of the Dulaimi tribe from Anbar province who was visiting Washington on Tuesday. He said Sunni tribes would refuse to fight alongside Iranian-directed Shiite militias that are being sent to Anbar. And he predicted it would take “at least a year” to organize a force that could liberate Ramadi with support of the local Sunni population.

The United States shouldn’t abandon its strategy: This is still Iraq’s war, not America’s. But President Obama must reassure Prime Minister Haider al-Abadi that the United States has his back — and at the same time give him a reality check. If Abadi and his Shiite allies don’t do more to empower Sunnis, his country will splinter. Ramadi is a precursor — of either a turnaround by Abadi’s forces or an Iraqi defeat.

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The Islamic State now controls Ramadi, a major city in Iraq. Here's why that matters and what to expect next. (Alice Li/The Washington Post)

Kimberly Kagan and Frederick W. Kagan: The fall of Ramadi was avoidable

The Post’s View: Obama’s weak Islamic State strategy

Marc Thiessen: Jeb Bush should focus on today’s Iraq

Max Boot: Strategy against Islamic State must be retooled