AILSA CHANG, HOST:
In the weeks leading up to the election, President Trump warned of a threat to national security. What he was referring to was a caravan of mostly Central American migrants moving through Mexico toward the U.S. border. He ordered thousands of active-duty troops to the border to support Customs and Border Protection agents, and most of these troops are already in place. And the first members of the caravan are just reaching the border.
In a moment, we're going to hear from NPR's Carrie Kahn on the Mexican side of the border. But first, we're going to go to NPR Pentagon correspondent Tom Bowman who's joining us in the studio now to talk about the border deployment. Hey, Tom.
TOM BOWMAN, BYLINE: Hello.
CHANG: So Defense Secretary Jim Mattis was on the border today. Tell us about his visit.
BOWMAN: Well, he visited active-duty Army troops outside McAllen, Texas, the far eastern portion of the Mexican border. And he defended the deployment as a way to help the Department of Homeland Security. That department asked for Pentagon assistance. Here's Mattis
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JIM MATTIS: I think that it's very clear that support the border police - or Border Patrol is necessary right now. If they come to me and say, we do not have the people to put in barbed wire; we don't have the capability to use helicopters to move people; we don't have the helicopters...
BOWMAN: Now, Mattis said troops have been sent to the border in the past going back several administrations, both Democrats and Republicans. But in almost all cases, they were National Guard troops and not active-duty troops. So Mattis didn't explain why that was necessary to send active troops. And of course, the president can immediately dispatch troops anywhere. That's why some on the Hill are calling this a stunt.
And it's funny, Ailsa, because I was talking with a senior Pentagon official just a few days before these deployments.
BOWMAN: And I said, hey, you guys sending troops to the border? I keep hearing the White House talking about that.
BOWMAN: And he said, it's not necessary. We have more than 2,000 Guard troops down there already helping the Border Patrol.
CHANG: Wow. I mean, the message that we're getting from the Pentagon during this deployment is that, quote, "border security is national security." But is that the same as saying this caravan represents some sort of threat to national security?
BOWMAN: Well, I think Mattis was talking in general terms. And he was careful not to be alarmist, as President Trump has been. The president called this an invasion. Mattis and others are not using those kinds of terms. But Mattis did say that Mexican police clashed with some in the caravan on the border between Guatemala and Mexico, so he is indicating it's a possible threat. But still, most American troops - active-duty troops will not carry weapons. Only MPs, military police, will carry weapons...
BOWMAN: ...We're told. And again, he said they'll likely be far away from any migrants.
CHANG: So if that's the case, what is the role of these active-duty troops if these migrants actually do overwhelm Customs and Border Patrol agents?
BOWMAN: Well, there's no sense of that yet. But again, they're in a support role, as Secretary Mattis said. And the Posse Comitatus Act prohibits troops from taking part in any kind of law enforcement activity. Of course, in addition to these troops heading down there, there's also more border police being sent to shore up these crossing points. So the sense is that they should be sufficient to deal with any sort of problem at these border crossings. And again, the military is also adding fencing, barbed wire and so forth, so that should help the situation.
CHANG: So how long are these troops going to be there?
BOWMAN: Well, Ailsa, the deployment is supposed to end on December 15, but they could be extended. We have no sense of that right now.
CHANG: So if these troops are down there indefinitely, I mean, how much is all of this going to cost? Are there any projections?
BOWMAN: You know, Secretary Mattis was asked about that today, the cost of this operation. He said we're still calculating the cost. So we have no sense, but we're talking millions of dollars or maybe even tens of millions of dollars. Any time you move this many troops and you have helicopters and cargo planes and so forth, it's a lot of money.
CHANG: That's NPR's Tom Bowman.
BOWMAN: You're welcome. Transcript provided by NPR, Copyright NPR.