Every time North Korea tests a rocket or gets closer to building a nuclear bomb, both China and the Western governments release a series of statements about how they're deeply concerned and threatening new sanctions against Pyongyang.

But have there been any official statements indicating a point of no return where an invasion into North Korea would begin? On one hand it is obvious launching rockets into the ocean is not enough to trigger a military operation. On the other hand a theoretical nuclear launch onto the Pacific coast of the US would obviously result in a heavy response. But where exactly is the line North Korea must cross?

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    What do you mean with "gets closer to building a nuclear bomb"? They already built one.
    – user2701
    Commented Aug 1, 2017 at 8:07
  • China has very little military presence in the Sea of Japan. IMO at least until China deploys their second or third carrier there, their ground invasion isn't really feasible in a practical way. Commented Aug 1, 2017 at 16:50
  • @BЈовић Do we know that? They've created nuclear explosions but that's not the same thing as building a bomb: for example, the world's first thermonuclear explosion was created by a device weighing 73 tonnes, which could hardly be called a "bomb". Commented Aug 1, 2017 at 19:38
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    @user3528438 is 1400Km long border not enough for a feasible ground invasion? Germany was pretty successful invading France/Poland with a way less border. Also Chinese army is incomparably stronger than NK's Commented Aug 1, 2017 at 23:28
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    @BЈовић They couldn't have a nuclear anything without a nuclear programme! But I've read many times that North Korea isn't known to have any nuclear weapon, i.e., something small enough to put in a missile. Commented Aug 2, 2017 at 8:33

2 Answers 2


But where exactly is the line North Korea must cross?

Line setting is generally acknowledged as a bad idea. For example, Barack Obama set a red line in Syria about chemical weapons. Then they used chemical weapons. And Obama looked like an idiot when he did not respond with military force.

Lines are bad for two reasons. One, they force action if the line is crossed. Two, they let the bad actor step almost to the line without worrying. We will ignore you unless you do such and such is not the best message to send. The bad actor can dance just on the other side of the line, daring you to react. Or if the goal is to get attention, they know that they have to cross the line. Thus setting a line may encourage crossing it under some circumstances.

On one hand it is obvious launching rockets into the ocean is not enough to trigger a military operation.

This is not at all obvious to me. Given that the stated reason for launching rockets into the ocean is to practice for shooting rockets at people, it seems the obvious time for military action to me. If we wait until after he has killed people or sold nuclear technology to terrorists, history will remember any military action as too late.

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    Could not agree more with your thoughts on red lines. Dancing close to a red line in itself should be seen as grounds for action. We also must not limit our options to military action, like sending in the Marines, although that remains an option. Economic, diplomatic, and military action short of an attack are also options (an example of the latter is drones for spying, which could also of course be used for attacks). Military action also comes in many flavors, from slap-on-the-wrist stuff to outright invasion. Commented Aug 1, 2017 at 18:12
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    I will point out that Obama asked for an authorization of use of military force, and this was rejected by Congress: en.wikipedia.org/wiki/… You could say that perhaps he should have done this before issuing the "red line" statement, but that's different than "you shouldn't make red lines", so much as "you should only issue red line statements taht you have the legal authority to act on" Commented Aug 1, 2017 at 20:30
  • "... [T]he stated reason for launching rockets into the ocean is to practice for shooting rockets at people..." Was this from an official North Korea statement?
    – user151841
    Commented Aug 1, 2017 at 22:28
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    " If we wait until after he has killed people or sold nuclear technology to terrorists, history will remember any military action as too late. ", Yup, so let's just kill a lot of people ourselves, so history will remember us as murderers. Fantastic logic!
    – Imean H
    Commented Aug 10, 2017 at 7:14
  • @JerrySchirmer - ... And the Congress refused to give Obama the permission to use force was EXACTLY to decrease his power and authority, even if it also hurts interests of USA. Commented Nov 15, 2020 at 17:27

The National Interest covers the invasion scenario nicely here. It is unlikely, due to the atomic weapons N Korea has, and probably a substantial supply of chemical weapons as well. The heavily populated city of Seoul is very close to the border, and would likely become a target of revenge with very high civilian casualties.

China recently positioned a higher number of troops on the N Korean border, but the purpose appears to be more to stop a mass emigration, than to invade.

Invasion? Doubtless, both the US and China have contingency plans for invading N Korea, but the chances either would actually do it are unlikely.

A more practical and safer scenario would be to kill Kim Jong Un. He has executed or driven off anyone of any real leadership ability in his government, so with his demise, there is no one who could step in and rally the troops to whatever the cause of N Korea might be said to be.

A precision strike is a possibility - Kim is still seen in public on occasion. One idea floated was to offer his military leaders a big bundle of cash and permanent residence in any western nation they choose, if they'd kill him and walk away.

It will be very interesting to see how the major powers handle this situation. When Kim threatens to use nuclear arms, he must be taken seriously. The results of the N Korea issue will have a large bearing on whether other semi-rogue states pursue nuclear arms. If the major powers can take out Kim without an invasion, they can demonstrate that nuclear arms do not protect the person who threatens to use them.

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    Seoul is about 40km (25 miles) from North Korea. Indeed, all of mainland South Korea is within about 400km (250mi) of the North. Commented Jul 31, 2017 at 18:40
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    I strongly disagree about the wisdom of attempting to assassinate Kim Jong Un because of the resulting chaos. Potential catastrophic outcomes include someone resuming the war with the south in an attempt to create a crisis severe enough that none dare challenge his control of the north (I recently saw an estimate of 200k civilian deaths for the 1st 12 hours of the war if a surprise attack required attempting to evacuate Seoul under fire), or an accidental shooting war between the US and China (both send special forces into the north to try and secure the nukes, and something goes very wrong). Commented Aug 1, 2017 at 14:43
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    @DanNeely Though I generally agree with you, I tend to distrust any kind of Seoul casualty estimates. I've seen them go as high as "at least two million", and as low as "a few thousand maximum even in the case of surprise all out artillery attack". I suspect even the involved militaries don't have much certainty.
    – mbrig
    Commented Aug 1, 2017 at 16:03
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    The problem here is that North Korea has little to lose, and South Korea has a sophisticated, wealthy society. With that in mind, I think the goal, and the strategy we have pursued thus far, should be to contain the North and let time do the rest. Should the North attack, they would be completely destroyed right away, but if it comes to that, everyone loses. Commented Aug 1, 2017 at 18:37
  • In addition to @DanNeely comment, the issue with assassination is what would happen if it succeeds. As bad as Kim Jong Un is, at least he is only one, relatively well known and certainly he does not seems to be the kind of guy that would throw away his luxurios lifestyle while he still has other options. What happens if after his death a civil war starts and the existing nuclear weapons end in the hand of several, unknown military leaders? What if some end in the hands of a "true believer" who really does not mind dying in retalation if he gets to hit S.Korea/USA? Too many unknowns.
    – SJuan76
    Commented Aug 1, 2017 at 20:23

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