War Stories

Why North Korea Is Test-Launching Missiles From a Submarine and a Train

And why it’s uniquely concerning.

Back of a man's head in the foreground and a TV showing a missile launch in the background
A man in Seoul watches footage of a North Korean missile test in September. Jung Yeon-je/Getty Images

In the last month, North Korea has test-launched seven different kinds of missiles. One of them carried a hypersonic glider, one was launched from a train, one was fired from a submarine, and another was a missile with the range to hit any spot in the United States. What is going on?

First, a few caveats. The North Koreans haven’t produced these missiles in large number (or, in most cases, any number). They haven’t loaded any of them with nuclear weapons and haven’t demonstrated an ability to make a nuclear warhead small enough to fit in a missile’s nosecone. Except for an experimental model, they haven’t built any submarines that can carry ballistic missiles. In other words, there’s no need to cower in a shelter just yet.

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One thing is clear: They’re not building up a first-strike capability. Or, if they are, the goal lies so far in the future, it’s not worth a moment’s thought, much less worry. More likely, they’re trying to make it very hard for the United States to launch a nuclear strike on North Korea.

They’re doing this in two ways. First, they’re making some of their missiles mobile—hence the launches from trains and submarines—so that the U.S. (or any enemy) would have a hard time finding, tracking, and hitting them. Second, they’re trying to ensure that we can’t nuke them without worrying that they will nuke us back—in which case we probably won’t nuke them in the first place.

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Probably nobody is musing that an American president might wake up one morning and launch a nuclear strike against North Korea. However, it is a reasonable concern that tensions might someday escalate between the U.S. and North Korea, to the point where a conventional war breaks out between the two countries. If that were to happen, the U.S. could exert great leverage by threatening to launch nuclear weapons. However, if North Korea also has nukes (even a few of them), and if some of them are mobile (meaning the U.S. couldn’t knock them out preemptively), then our nuclear card loses its trump value.

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In other words, North Korea is doing what all nuclear powers are fundamentally doing—trying to deter a nuclear attack. This isn’t a purely defensive strategy. A deterrent can be used as a cover for non-nuclear aggression. In any case, as many small nuclear powers have learned over the years, it doesn’t take a lot of nuclear weapons to pull this feat off.

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North Korea is stepping up its nuclear-missile programs possibly in response to the U.S. missile-defense program. Let’s say North Korea thinks it needs 10 nuclear-armed missiles to deter an attack. And let’s say the U.S. has the ability to shoot down 50 nuclear missiles. (I’m making up these numbers; they are for illustrative purposes only.) North Korea might, therefore, think it needs 60 missiles to ensure that 10 of them get through the defenses. (This may be why China is upping its nuclear programs as well.)

There are two uniquely concerning things about a North Korean submarine-launched missile. First, latching a missile to a submarine means you can extend the range of a missile and makes it easier for North Korea to attack the United States—again, assuming it one day builds the missiles and a submarine that can go out that far. Second, a submarine can sneak right up to an adversary’s shore, underwater, and launch a missile with next-to-no warning. Japanese officials are particularly worried about this—which is making some of them contemplate building a missile-defense system, or its own offensive nuclear arsenal, either of which might drive North Korea to build more offensive missiles.

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But the experimental submarine model North Korea has built is very noisy; it’s also diesel-electric, which means it can’t go very far without coming up to the surface or disappear the way that modern nuclear-powered submarines can. However, this isn’t entirely reassuring. One can imagine a scenario where a North Korean submarine is surrounded, and the captain onboard fires his missiles, on the premise that he either uses them or loses them. It’s also possible that the North Korean leader might not allow a submarine crew to roam too far from home, out of fear that they’ll defect.

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The main point of all this is that nuclear-armed nations build up their arsenals, at least in part, as responses to what their nuclear-armed rivals are doing—or at least to what they think those rivals are doing. For instance, test data suggest that the U.S. missile-defense program has little ability to shoot down long-range ballistic missiles. However, intelligence agencies tend to exaggerate an enemy’s strength, and to devise worst-case scenarios, as justification for their own programs. So it may be no coincidence that North Korea tested a submarine-launched ballistic missile just one month after South Korea did the same.

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In that sense, domestic politics also play a role. Kim Jong-un has put renewed emphasis on his missile program. It’s very expensive. He justifies the expense with propaganda that North Korea is surrounded by enemies who are hellbent on destroying the people’s paradise. He therefore cannot allow South Korea, in particular, to eke out an edge in the arms race without matching it as quickly as possible.

Two larger inferences can be derived from all this. First, there is no way North Korea will ever dismantle its missiles or its nuclear weapons. They are all that the regime has—as a token of strength and, less symbolically, as a deterrent to foreign attack. The official U.S. position—that North Korea must agree to “complete, verifiable, irreversible de-nuclearization”—is a pipedream. If we want to lower tensions, and reduce the threats to our regional allies, through negotiations, we have to devise a different formula.

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Second, back in April 2009, just months into his presidency and during his first foreign trip to Prague, Barack Obama made this lofty pronouncement: “To put an end to Cold War thinking, we will reduce the role of nuclear weapons in our national security strategy and urge others to do the same.” It hasn’t happened. All countries that had nuclear weapons back then—including the United States—are planning to improve or embellish their arsenals. Other countries, which have long had the ability to make nuclear weapons but have held back for one reason or another, are thinking of diving in. One reason for this is that the world has become a more turbulent, anarchic place. Countries that had once been assured by the U.S. “nuclear umbrella”—the pledge that Washington would use its own nuclear weapons in response to an attack on its allies—are less convinced that we’d make good on that promise and are, therefore, thinking of hoisting their own umbrellas to guard against a hard rain.

North Korea’s missiles are only the most glaring signs of danger on the horizon, and not necessarily the most ominous. Things are unsnapping all over. It will take some brilliant thinking and even more brilliant diplomacy to put them back together or to fashion some new international system to make the world more secure.

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