Islamic State of Iraq and Syria - ISIS

Levi Shirley was an American who volunteered to fight alongside the Kurdish YPG against ISIS before his death in July 2016.

Retired Army Gen. Raymond Thomas joined a list of former officers who have questioned the withdrawal of U.S. troops.

Trump also said it was highly unlikely that the presence of the weapons would lead to a confrontation with Turkey.

The decision comes amid the chaos of Turkey's invasion into northern Syria.

Top brass weren't blindsided by recent events, officials now say.

"We have to always be concerned with this," the former defense secretary said.

"We have reports already of indiscriminate fire landing near American forces," Defense Secretary Mark Esper said.

Turkish officials say the U.S. position was not targeted.

The stop comes in response to threats from Turkey.

Coalition aircraft can still come to the rescue of ground troops even as Iraq recently enacted airspace limitations.