The American-backed Iraqi effort to oust Islamic State militants from their stronghold in Fallujah turned out to be far easier than many U.S. officials initially feared.

“Once they got through the hard-candy shell and into the chewy center, things went much more quickly,” Pentagon spokesman Jeff Davis said Monday. “It was really a heavy fight along the front line. But once they penetrated that, it seemed to go very quickly.”

The five-week operation officially ended Sunday when top Iraqi commanders declared the city “fully liberated” from ISIS.

Retaking Fallujah was not the grinding block-by-block street fight that the Iraqis faced in Ramadi last year, an operation which took almost four months to complete. Yet by comparison, the Iraqi operation in Fallujah took far longer than a similar battle the U.S. Marines fought there in November 2004, known as Operation Phantom Fury, when American military officials declared the city cleared after nine days.