AUDIE CORNISH, HOST:
The last ISIS stronghold in Syria fell to U.S. and Kurdish forces a year ago this month, but there are still hundreds of U.S. service members in the country. And their new mission is keeping the country's oil fields away from Syrian and Russian forces. NPR's Tom Bowman is in Syria. Earlier today, he went along on an American patrol charged with protecting those oil fields. Tom, can you just give us a better sense of where you are and about the mission itself?
TOM BOWMAN, BYLINE: Well, Audie, I'm in northeast Syria, and I can't say exactly where for security reasons. And today we drove for hours in a large armored convoy along these country roads. You can see the fields stretch into the horizon - really, the size of Vermont. And ISIS at one time used these oil fields to make millions of dollars to finance their caliphate.
CORNISH: And now I understand that those same oil fields actually came under attack. What have you learned so far?
BOWMAN: Right. Well, actually, it was a multiday attack on two of the oil fields, the first one since the U.S. mission began last fall to protect the oil fields. There were soldiers from the West Virginia National Guard at one of the fields. And early Wednesday morning, a drone carrying a mortar dropped it near where they were sleeping. No one was injured, and the soldiers quickly drove off the base.
But this morning, the drone returned again before dawn and dropped several more mortars. And you could see the big circular holes in the ground, pockmarks on the U.S. military trucks and one on one of the oil tanks. And we talked to Sergeant 1st Class Mitch Morgan (ph) of the West Virginia National Guard, who was there.
MITCH MORGAN: We immediately sprung, got in the vehicle. I got a REDCON-1 status. We were out in 2 minutes. We came out this way. As we were going out, they was raining mortars in on top of us.
BOWMAN: And then, Audie, just tonight, we heard that several drones returned to that site where the West Virginia National Guard is based. There's no word yet on any sort of mortar rounds coming in. But an interesting thing about these mortars is that some of them, we're told by Army investigators, were made with 3D printers, which means that obviously someone pretty sophisticated put together these mortars, perhaps a nation-state.
CORNISH: Help us understand the mission here. Why is the U.S. trying to bar Syria from these oil fields? Obviously, Syria has had trouble holding onto them - right? - through all of this fighting.
BOWMAN: Right. The U.S. and Europe actually want Bashar al-Assad removed. He killed hundreds of thousands of his own people in a civil war. And they don't want Assad to gain more strength by having access to millions of dollars from the oil. And Russia is Syria's main ally. The U.S. ally in this ongoing ISIS fight, the Kurds, are using proceeds from the oil to continue their operations. And to make this even more politically convoluted, the Kurds are selling the oil to the Syrian government.
CORNISH: In the meantime, Syrian and Russian forces obviously have an interest here. How are they responding to the moves by the U.S. convoy?
BOWMAN: Well, there was a deadly incident involving the U.S. forces recently with pro-Syrian regime militia. The U.S. killed one, maybe two while on a patrol. And also, there's Russian harassment of the U.S. convoys. The U.S. tried to block them, but nothing deadly has happened. Neither side wants this to escalate any further.
CORNISH: All right. So what happens then? I mean, could this trigger a possible wider conflict with the U.S.?
BOWMAN: Well, it's unlikely. And many observers, both the U.S. and Kurdish officials, believe that once Idlib is pacified - and that, of course, is the area of northwest Syria that the government of Assad is trying to pacify - that once that comes to an end and Assad basically recaptures Idlib, the Kurds will strike a deal with the Syrian regime. They're actually hoping for more autonomy. We're not sure if they're going to get that or not. And once that happens, Audie, once they sign a deal with Assad, the sense here is the last U.S. troops will leave.
CORNISH: That's NPR's Tom Bowman in northeast Syria.
Thank you so much, Tom.
BOWMAN: You're welcome, Audie. Transcript provided by NPR, Copyright NPR.