U.S. Army infantry units and armored vehicles have moved into Syria to guard oil fields in the northeastern part of the country, following a successful U.S. Special Operations Forces raid that killed the leader of the Islamic State of Iraq and Syria.

Army Col. Miles Caggins III, spokesman for Operation Inherent Resolve (OIR) in Iraq, sent out a tweet Thursday showing images of M2A2 Bradley fighting vehicles being loaded onto C-17 Globemaster aircraft to support the oil field mission near Deir ez-Zor, Syria.

The tweet names the North Carolina National Guard's 4th Battalion, 118th Infantry Regiment, 30th Armored Brigade Combat Team, as the unit selected for the mission. The 4-118 is attached to the South Carolina Guard's 218th Maneuver Enhancement Brigade.

On Monday, soldiers with Alpha and Bravo Companies, 4-118, conducted bore sight and zeroing procedures of their M1 tanks at the Udairi Range Complex in Kuwait, according to the unit's Facebook page.

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OIR spokeswoman Maj. Mayra Nanez confirmed that Caggins' tweet is accurate.

"They are in Syria," Nanez said, adding that it's currently unclear whether other units will follow.

Defense Secretary Mark Esper said Monday that sending mechanized forces and other forces is necessary to protect the oil fields. He spoke at a Pentagon press conference following the U.S. Special Operations raid Saturday that killed Abu Bakr al-Baghdadi, the founder and leader of ISIS.

"Despite Baghdadi's death, the security situation in Syria remains complex," he said. "Multiple state and non-state actors continue to vie for control of territory and resources within the country."

At the height of Baghdadi's reign, the oil fields provided ISIS with the bulk of financial resources used to fund its terror campaign, Esper said.

The oil fields also provide a critical source of funding for the Syrian Democratic Forces, which conducted the lion's share of fighting against ISIS forces, and will help the SDF to secure ISIS' prison camps and conduct operations against ISIS, he added.

"U.S. troops will remain positioned in this strategic area to deny ISIS access to those vital resources, and we will respond with overwhelming military force against any group that threatens the safety of our forces there," Esper said.

U.S. forces withdrew from northern Syria in early October to avoid clashes with Turkish forces, which launched an invasion into the country Oct. 9.

-- Matthew Cox can be reached at matthew.cox@military.com.

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