Update to this story.

(AP) – Iraqi troops abandoned dozens of U.S military vehicles, including tanks, armored personnel carriers and artillery pieces when they fled Islamic State fighters in Ramadi on Sunday, the Pentagon said Tuesday.

A Pentagon spokesman, Col. Steve Warren, estimated that a half dozen tanks were abandoned, a similar number of artillery pieces, a larger number of armored personnel carriers and about 100 wheeled vehicles like Humvees. He said some of the vehicles were in working condition; others were not because they had not been moved for months.

This repeats a pattern in which defeated Iraq security forces have, over the past year, left behind U.S.-supplied military equipment, prompting the U.S. to destroy them in subsequent airstrikes against Islamic State forces.

Asked whether the Iraqis should have destroyed the vehicles before abandoning the city in order to keep them from enhancing IS’s army, Warren said, “Certainly preferable if they had been destroyed; in this case they were not.”

Warren also said that while the U.S. is confident that Ramadi will be retaken by Iraq, “It will be difficult.”