Defense Secretary Mark Esper warned that the "security situation in Syria remains complex" after the killing of ISIS leader Abu Bakr al-Baghdadi over the weekend by U.S. special forces, since state-sponsored and non-state entities are vying for control of northern Syria's resources.

Esper and Chairman of the Joint Chiefs of Staff General Mark Milley briefed reporters Monday at the Pentagon on the operation resulting in the death of al-Baghdadi.

Video of al-Baghdadi's final moments exists. "We have video and photos," Milley told reporters, though those images aren't being released yet. He indicated that once they're vetted and declassified, some video and images may be made available.

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Asked about al-Baghdadi's body, Milley did not offer specific details, saying only that it had been dealt with in accordance with standard operating procedures. After Osama bin Laden was killed, his body was buried at sea.

The defense secretary said that acting as a police force to solve every dispute "is not our mission." He went on to say that the U.S. mission remains the same as it was in 2014, the enduring defeat of ISIS. Esper went on to say that the recent repositioning of U.S. forces in Syria was intended to give the president options.

Esper reiterated to reporters that the oil fields in the region were secured, and he suggested that they would be protected against ISIS and used instead to help fund the Kurdish Syrian Democratic Forces as they continue to conduct operations against ISIS. The defense secretary also said that he spoke with U.S. allies at a NATO conference last week and reiterated the U.S. commitment to defending against ISIS and called on them for help in the mission. He also said that Turkey still bears responsibility for what he called its "unwarranted" incursion into northern Syria, "which has brought further instability to the region."

Milley was also asked about President Trump's characterization of al-Baghdadi's final moments as "whimpering." He suggested that the president may have spoken to unit members about al-Baghdadi, but Milley said he has not yet spoken with unit members who carried out the mission.

There were no U.S. fatalities in the operation, but a military dog that took part in the mission was injured. Milley and Esper declined to release the name of the dog, but praised it and said it had been "slightly wounded" and is expected to make a full recovery. The dog is back in theater, Milley said.

The Sunday raid by U.S. commandos in northwestern Syria ended a yearslong manhunt for Abu Bakr al-Baghdadi, the most wanted terrorist in the world.