DAVID GREENE, HOST:
North Korea's leader, Kim Jong Un, and President Trump have been trading threats and personal insults. It's even gotten to who has the bigger nuclear button. Now, the U.S. secretaries of state and defense insist that despite that, they are still pursuing diplomacy. But that does not mean the United States is not preparing for a different scenario.
Here's Defense Secretary James Mattis speaking last fall.
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JAMES MATTIS: Now, what does the future hold? Neither you nor I can say, so there's one thing the U.S. Army can do and that is you have got to be ready to ensure that we have military options that our president can employ if needed.
GREENE: Military options when dealing with North Korea. Those are some pretty strong and important words that we should explore more with NPR Pentagon correspondent Tom Bowman, who's here. Hey, Tom.
TOM BOWMAN, BYLINE: Hey, David.
GREENE: So what have you been looking at? Are there actually options being, I mean, considered for North Korea?
BOWMAN: Well, one of the things the Army is doing is training many more soldiers, thousands more soldiers, in tunnel warfare. Now, usually, the Army has one or two brigades - and a brigade is about 4,000 soldiers - trained in this kind of activity. They want to double, maybe even triple the number of soldiers because North Korea is basically honeycombed with tunnels and bunkers, thousands of them.
And this is all an effort just to get ready should the president say, it's time for military action against North Korea.
GREENE: So for decades, the north has been - what? - building this network of tunnels anticipating a possible war with the south or the U.S. or somebody?
BOWMAN: Absolutely. They bury chemical, biological weapons in these tunnels. They have some for troops. They're miles long, some hundreds of feet deep. Nuclear weapons can be put in these tunnels. Even artillery...
BOWMAN: ...Can be put in these tunnels and rolled out when need be. Now, they've discovered some of these tunnels under the demilitarized zone and some have even gotten closer to Seoul. One is now a tourist site in Seoul that people can go into.
GREENE: I also went to the demilitarized zone. There's a tunnel you can go down right up to the North Korean border. Is that one of these tunnels, too? I mean, it's...
BOWMAN: I'm not sure if that's one, but it could be.
GREENE: Maybe they've recreated it. But I'll certainly go there next time and it won't be as much fun with all these tensions that are there. How much does the U.S. know about these tunnels? It's not like this is a country that, I presume, they can get a ton of intelligence from. I mean, do they have a good sense of what these tunnels are like, where they are? How much prep can they actually do?
BOWMAN: Well they can see from satellites some entrances and exits from some of these tunnels. They know there are thousands of them and, again, hundreds of feet deep.
But again, if there is military action against North Korea - and some of them are so deep, you're going to have to send soldiers, U.S. soldiers, South Korean soldiers, into these tunnels to either, you know, find nuclear weapons or chemical and biological weapons because they're so far underground, they're going to be, you know, not be able to be taken out by bombs or missiles.
GREENE: Totally different kind of warfare it sounds like.
BOWMAN: Absolutely. And I'm told that the soldiers from the 101st Airborne and the 82nd Airborne are among those soldiers to have to get this kind of training. They've also bought specialized equipment, bolt cutters, acetylene torches, special night-vision goggles because in the tunnels, there's no ambient light, special radios as well.
And they're going to be training throughout 2018. But I think it's important to note that this is just getting ready. Defense Secretary Jim Mattis has said the Army must be ready. This does not mean that the U.S. is inching closer to war. It means, as Mattis said, the Army has to be ready if the president needs options.
GREENE: OK, so this is the kind of thing that might go on with different scenarios that the military is considering around the world.
GREENE: But it is noteworthy that they are specifically looking at the situation in North Korea and what the U.S. military could confront.
BOWMAN: Right. And the Army's doing this quietly. They're not basically coming out and putting out press releases about this training.
GREENE: That would probably not be the best idea.
BOWMAN: Right. It is very quietly being done.
GREENE: NPR Pentagon correspondent Tom Bowman. Tom, thanks.
BOWMAN: You're welcome, David.
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