Story highlights U.S. didn't have "crystal clear idea" who hostages were, Pentagon spokesman says

Hostages "faced imminent mass execution," according to Pentagon

70 hostages were liberated in the operation, officials say

(CNN) The Pentagon identified the U.S. Army soldier who died as part of a rescue mission in Northern Iraq earlier this week as Master Sgt. Joshua L. Wheeler, of Roland, Oklahoma.

About 70 hostages facing "imminent mass execution" were rescued in the operation at an ISIS-controlled prison that killed Wheeler, 39, according to a Pentagon statement.

Wheeler, who was was part of the Army's Delta Force and assigned to Headquarters of the U.S. Army Special Operations Command at Fort Bragg, North Carolina, is the first American to die in combat in Iraq since November 2011.

Master Sgt. Joshua L. Wheeler

The hostages he was helping to rescue included more than 20 members of the Iraqi Security Forces, local residents and several ISIS fighters accused of spying. They were liberated Thursday after a helicopter assault that involved U.S. special operations troops as well as Kurdish and Iraqi forces, U.S. officials said.

"There was not a lot of time," one U.S. official told CNN on condition of anonymity. "The threat of execution was imminent."

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