By late last year, classified American intelligence reports painted an increasingly ominous picture of a growing threat from Sunni extremists in Syria, according to senior intelligence and military officials. Just as worrisome, they said, were reports of deteriorating readiness and morale among troops next door in Iraq.

But the reports, they said, generated little attention in a White House consumed with multiple brush fires and reluctant to be drawn back into Iraq. “Some of us were pushing the reporting, but the White House just didn’t pay attention to it,” said a senior American intelligence official. “They were preoccupied with other crises,” the official added. “This just wasn’t a big priority.”…

A reconstruction of the past year suggests a number of pivotal moments when both the White House and the intelligence community misjudged the Islamic State. Even after the group’s fighters stormed across the border into Iraq at the start of the year to capture the city of Falluja and parts of Ramadi, the White House considered it a problem that could be contained.

Intelligence agencies were caught off guard by the speed of the extremists’ subsequent advance across northern Iraq. And the government as a whole was largely focused on the group as a source of foreign fighters who might pose a terrorism threat when they returned home, not as a force intent on seizing territory.