WASHINGTON--U.S. forces in Iraq were attacked Dec. 27 near Kirkuk by Kataeb Hezbollah, a group with links to the Islamic Revolutionary Guard's Quds Force. The attack, which involved 31 rockets fired, killed one American civilian contractor and injured four American service members as well as two partners in the Iraqi security forces, Defense Secretary Dr. Mark T. Esper said.

"The U.S. military responded, and took defensive actions by striking KH bases in western Iraq and western Syria, striking a combination of the command and control [center] or weapons caches with considerable effect," Esper said during a press gaggle in the Pentagon today. "The attacks were quite successful."

In the wake of the KH attack, the defense department has deployed an infantry battalion — about 750 soldiers — from the Immediate Response Force of the 82nd Airborne Division to the U.S. Central Command area of operations. Additional forces from the IRF prepared to deploy over the next several days, the defense secretary said.

"They are deploying to the region to, on order, reinforce our facilities and to protect our personnel in the region as called upon, and obviously they have the capability to perform other missions as well, as need be," Esper said.

Chairman of the Joint Chiefs of Staff Army Gen. Mark A. Milley described the forces from the 82nd Airborne as a "general-purpose unit," on a defensive mission, adding that such a unit exists precisely for the types of situations it was called upon to respond to.

"It's going over there, it's going to be in Kuwait, and they may have follow-on missions in other places," Milley said. "But their purpose is defensive in nature, to defend U.S. personnel, equipment and facilities."

The chairman said other U.S. forces have been alerted, though no decision has yet been made to deploy those forces. "But there are a variety of forces that are alerted and prepared if necessary depending on the situation, as we move forward," Milley said.

Esper said "provocative behavior" by Iranian-backed Shia militias has been ongoing for several months. The Dec. 27 attack was the latest, he said, adding that while he believes the attacks may continue, the U.S. is ready.

"They've been shooting rockets, indirect fire, any type of things, attacking our bases for months now," the defense secretary said.

"In the last two [months] alone we've [had] nearly a dozen attacks against U.S. forces, against our coalition partners. So do I think they may do something [else?] Yes. And they will likely regret it. And we are prepared to exercise self-defense, and we are prepared to deter further bad behavior from these groups, all of which are sponsored, and directed and rescued by Iran," Esper said.

Read the full transcript from the media engagement.

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