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No boots on the ground. Except, of course, there are.

(CNN)The Marine killed in an ISIS rocket attack in Iraq on Saturday was at the first American firebase that had only become operational a few days earlier CNN has learned.

The existence of the firebase had not been made public. The Pentagon had planned to acknowledge the firebase this week, a defense official tells CNN.

The rugged location for now has a “couple of hundred” Marines living in tents near Makhmour in northern Iraq. It’s assumed ISIS observed the Marines moving into the area and saw them firing practice rounds with their howitzers, the official said.

ISIS on Saturday fired two rockets from about 15 km away. One fell inside the base killing one Marine and wounding several others. The Marines returned fire with their artillery.

On Sunday, the Pentagon identified the slain Marine as Staff Sgt. Louis F. Cardin, of Temecula, California. Cardin was assigned to the 2nd Battalion, 6th Marine Regiment, 26th Marine Expeditionary Unit, Camp Lejeune, North Carolina, the Pentagon said.

The Pentagon has yet to formally acknowledge it has established its first U.S. fire base in Iraq in the current fight against ISIS for what the official said will eventually be a limited ground combat operation in support of the Iraqis.

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