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There's an article in the Japanese constitution forbidding the country from going to war. The country nonetheless maintains a substantial self-defence force.

I'm wondering if Japan can feasibly disband the self-defence force and rely only on nuclear deterrence. The idea is that since they will only have nuclear weapons, they would not be able to intervene internationally in limited fashion. In other words, this would effectively force the country to adhere to its constitution. From another angle, doing this also means that if another country attacks them, they can only retaliate with nuclear weapons - there is no chance that they "react proportionally" in a conventional war, and therefore attacking them might be too costly. There's also an advantage in cost: the self-defence force currently has a budget of ~US$50 billion per year, while the UK's Trident program (which is the UK's nuclear deterrent) only costs ~£2 billion per year.

Doing this would involve developing nuclear weapons, but Japan is a nuclear latent state so this should be straightforward.

Is this feasible? If so, has it been suggested? If not, why not?

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    Besides JJJ's quite good answer, I would also think that Japan, due to being the only country ever to have been bombed by atomic weapons, and due to their aversion to military affairs, would be the last country to pursue this state of affairs, at an emotional/sell-it-to-the-electorate level. Because the very nature of this defense posture is that you might need to go nuclear, otherwise it's just not credible as dissuasion. And that means "selling" not just war, but nuclear war as a policy to your electorate. That's a hard sell to an antiwar country. May 14 at 6:35
  • A nuclear weapons program would plausibly allow reduction of conventional forces, although not their complete elimination. Whether there would be a cost savings is another question, as a nuclear deterrent has to have a bunch of expensive features, like ideally surviving commando raids, first strikes, and so forth. In the case of Japan, I suspect the real reason they have not developed nuclear weapons is because the US is providing something of value in exchange, obviously the military protection but probably also economic concessions. (recall 1980s rivalry).
    – Pete W
    May 14 at 13:53
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    Japan is a signatory of the Non-Proliferation Treaty and as such has pledged to not acquire nuclear weapons. Leaving the treaty to become a nuclear weapons state would put it in the same league as North Korea. May 14 at 15:17
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    Japan's self-defence force keeps over 200 000 people directly employed and is available for things like assistance with disasters, so you'd have to find something else for those people to do, and for the people no longer supplying the JDSF, and keep more trained people available for emergency work than just the normal emergency services. I don't know the monetary cost of that. May 14 at 19:16
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From another angle, doing this also means that if another country attacks them, they can only retaliate with nuclear weapons - there is no chance that they "react proportionally" in a conventional war, and therefore attacking them might be too costly.

But that goes both ways, would the defending country resort to a nuclear strike in response to a small attack or in case of a small war? The answer is no, because such a disproportionate response would be an act of extreme aggression. That would make the defending country which has launched nuclear weapons the aggressor (the first to escalate to a nuclear war).

Potential attackers can abuse that reluctance of the defending country to go nuclear by employing salami tactics. Such hesitation is illustrated by this Yes, Prime Minister clip in which the fictional UK Prime Minister is asked when he should launch nuclear missiles in response to a potential Russian invasion of Western Europe. Salami tactics refers to taking small slices in a broader conflict. Individual slices would be chosen by the attacker to get ahead in a broader offensive without provoking an unwanted response (sanctions, a military response, a nuclear response).

A practical example of such a conflict takes place in the South China Sea. Through different tactics (diplomatic, economic, militarily), China is able to strengthen its position in the South China Sea. None of the individual actions warrant a military response, but combined they are enough for European and American navy ships to patrol the area. That's using expensive military equipment (navies) as a deterrent.

If you only had nuclear weapons then you'd be nowhere. You could fire them in the South China Sea, but that won't achieve anything positive. And firing them at China would start a nuclear war. So without a conventional military, you'd be unable to stop such intrusions.

Of course, in this example there's a united effort to keep the South China Sea accessible as the international waters they are. While it's a local issue, it affects the international community because many shipping routes pass through there. When there's only a local issue, then you cannot rely on the international community coming through to defend you.

Even if you have an understanding with a superpower to defend you, which Japan has with the US, it's always a dependent relationship. For example, the superpower can try to renegotiate the understanding when it feels like it, as the US did in 2019.

I should say that such alliances aren't uncommon for very small countries. Wikipedia has a list of countries without armed forces. Many of these countries are under the protection of a larger neighbor.

In conclusion, nuclear powers without a conventional military lack the versatility to engage in regular conflicts. That means such a defense strategy would have to rely on alliances.

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    Potential attackers can abuse that reluctance of the defending country to go nuclear by employing salami tactics wouldn't that be kind of the point though? Treading on the country's toes would be dangerous, viz in the situation in the South China Sea, China would have to be careful, or the other countries might decide to press the button (if they had nuclear weapons). They can't respond with navy patrols that would be an indication it's time to back off, they can only respond with thermonuclear war.
    – Allure
    May 14 at 8:13
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    @Allure I think it's hard to explain it any better than the "Yes, Prime Minister" clip linked in the answer does. Should the Japanese launch nuclear missiles as soon as a Chinese gunboat gets within the 3 mile zone of one of the contested islands in the sea between China and Japan? Kill millions of civilians because what could be a navigation error about a conflict history might decide Japan is wrong about? When your answer is no, when would they launch nukes?
    – Philipp
    May 14 at 8:55
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    @Allure ...and when the Chinese misjudge the red lines drawn by the Japanese, then millions of Chinese and Japanese citizens will die. Do you think that's a good solution?
    – Philipp
    May 14 at 14:41
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    @JJJ I'd add that a superpower with enough capabilities to nuke the planet doesn't need an alliance. And one part of the question hinges on the possibility to convince everyone that any minor infraction triggers a nuclear war and thereby works as a deterrent against a salami tactic. Not having conventional forces might help to re-enforce that assumption, exactly because nukes are the only option you have, the dilemma goes both ways: If the salami thief believes in you being "crazy" enough to follow through for any violation, they are also deterred from stealing salami (on purpose). May 14 at 16:37
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    "I'd add that a superpower with enough capabilities to nuke the planet doesn't need an alliance. " This is a ridiculous statement. Nuking the planet will ruin the biosphere. What if the enemy is internal? Or the issue is a border conflict? How do you secure resources, if all you can do is destroy them? The USA has this capability. Without the military, what's to stop Canada from invading? Most of the Canadian population lives very close to the border, you see a massive mobilization in Southwester Ontario, how do you plan to nuke it, but not New York?
    – chiggsy
    May 15 at 5:49
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There is no such thing as an nukes-only military forces.

One needs a small army just to guard the nukes against someone else sabotaging them or, worse, abusing them in some way. Nukes also don't just appear out of thin air, they need a whole industry to create and maintain them. This industry is profoundly entangled with military structures as well.

In periods of deteriorating economy and/or internal conflicts (these inevitably touch the military forces), some countries struggle with keeping their nukes safe (see Russia in 90's) or outright give up on having nukes (Ukraine in 90's)

That's why one can have nukes only after having more or less adequate "conventional" army forces.

Then again, there is a whole specter of military tasks where no single state actor may be designated as an enemy. What about a powerful terrorist group (it may as well be home-grown)?

One can always create stronger police forces, but they will be an army in any aspect other than the name.

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No, it wouldn't, and the reasons are the following:

First, that would only work if the opponents believed that the nation that had the nuclear weapons would be willing and able to use them. So, minor provocations that were below the "threshold" of what a reasonable country would be willing to use nuclear weapons for would not be deterred by their nuclear arsenal. Also, immediate neighbors might suspect that they'd be unable to launch an attack without risking "blowback" on themselves or their allies.

Secondly, you need to consider how such a country would defend itself from other nuclear countries. As I said above, nuclear weapons are only a deterrent if the other side believes that you're willing and able to use them. If you used a nuclear weapon against another nuclear state (or another country that was closely affiliated with a country that had them), they'd presumably simply retaliate with their own nuclear weapon strike.

In fact, if they believed that the country in question was about to launch a nuclear attack, they could simply launch their own preemptive nuclear strike in an effort to incapacitate them. (This is especially the case given that the country's only offensive weapon is nuclear weapons, so if they attack at all it'll be nuclear). Even a country that had only conventional weapons would likely have little to lose by launching as many conventional strikes as possible if they believed that a nuclear strike was imminent anyway.

Finally, you also need to consider actions like an opponent stealing, disabling, or destroying their nuclear weapons by non-nuclear means. Without a sufficient conventional military to protect the nuclear weapons, that could be easier than you'd think. What's to prevent a foreign nation from staging a middle-of-the-night ambush to take over the weapons site?

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  • "how such a country would defend itself from other nuclear countries." - yes, key point!
    – Pete W
    May 14 at 14:13
  • I'm surprised that both answers focus on countries as opponents. I'm equally surprised that terrorist groups and small countries aren't operating nuclear weapons already, which is a topic related to the difficulty of stealing any. Hey, am I allowed at least a car and a knife while I'm patrolling the silo? May 14 at 15:49
  • @JirkaHanika " I'm equally surprised that terrorist groups and small countries aren't operating nuclear weapons already", they don't? Did something happen?
    – Dan M.
    May 14 at 16:17
  • who is to say there is only one site to take over? ;P Though if all you need is a defence force strong enough to secure one nuke silo long enough to fire it, that is an amendment OP likely would accept. I guess OP is also fine with having enough conventional forces to operate radar and reconnaissance... but that thought of line also leads to interesting consequences... how do you do reconnaissance ... that's another big chunk of "conventional military forces". Because you need to know who attacked you in order to nuke the right place ;) May 14 at 16:52
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    Last I saw, the Trident (which is the UK's nuclear deterrent) is maintained by having one submarine constantly on patrol in an unknown area of the world's oceans. This deters attackers, because even if one turns the UK itself into nuclear wasteland, one cannot disable the submarine which can retaliate. en.wikipedia.org/wiki/Trident_(UK_nuclear_programme)#Operation
    – Allure
    May 17 at 0:52
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The bulk of the problem isn't deterrence but how you use them in such a way that you suffer no consequences.

Let's say that China launches a full strike on the US and the US just shrugs and takes it on the chin. The US is gone, a nuclear wasteland. So China wins, right?

All those nukes blowing up in midair (air burst) will release lots of dust. Some of it will be the nuclear material, but a lot of it will be common dust. Add in all the nuclear fires after your strike is over and you're looking at a ton of material ejected into the atmosphere. Assuming the nuclear material doesn't make it worldwide (and that's a huge if), the dust will, and it will be devastating

In that extreme scenario, the researchers write, a cloud of black soot could envelop the sky, causing temperatures to fall dramatically. Key agricultural hotspots would lose the ability to grow crops, triggering a global famine.

"It would be instant climate change," Alan Robock, an author of the study, told Business Insider. "Nothing like this in history, since civilization was developed, has happened."

In other words, that strike would wipe out China's foe... and then China would have to suffer with the resultant climate change. It would be the penultimate pyrric victory.

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  • I think you're missing out on the point that quite a lot of nations would actually quite like their climate to change. Russian, for example, has a lot of icy desert that could be farmed if the world warmed a few degrees.
    – Valorum
    May 15 at 17:44
  • This applies to all nuclear weapons, no? I thought the ability to guarantee that any attacker will themselves suffer horribly if they attack is how deterrence works. It doesn't mean you suffer no consequences, you surely do, it's just that any attacker also suffers just as badly.
    – Allure
    May 17 at 0:55
  • @Allure No, the main threat of deterrence is that the other side responds in kind. My point is that, even if they don't, you're still screwed.
    – Machavity
    May 17 at 2:34
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The other answers have explained that the problem with conventional nuclear weapons is the step up of "going nuclear" being disproportionate. However, nuclear weapons need not be high powered.

In the case of Japan, low and high power nuclear weapons alone would probably not be a sufficient independent defence, because the seas are a significant resource, notably for food, along with a small land area not able to sustain tit-for-tat attacks that are described below. Theoretically if your country was large enough, then low level nuclear tactics could provide a deterrent. The demonstration of the ability, and willingness, to perform low-level nuclear attacks on enemy countries could be sufficient deterrent to prevent attack.

At their lowest power, nuclear weapons can target individuals/families: for example a Russian dissident was poisoned with nuclear materials smuggled into London. These could be delivered by agents, and/or by proxies, such as domestic terrorists.

Larger levels of nuclear contaminants can be used to poison food/water sources, fuel distribution networks, places of cultural/religious/ecological significance, or urban areas. Dirty bombs with varying levels of radioactive contaminants could delivered by agents or by rockets.

EDIT: As I have already mentioned, and commentators didn't understand, these tactics would not be effective for a country with a small land area because of the inability to sustain tit-for-tat exchanges which I foresaw might result when the origin of attacks was discovered, another thing the commentators misunderstood. Indeed the origin of these measures used for defence would be immediately obvious since they would be deployed as retaliation for a previous attack. There has been no military retaliation for the Russian poisonings on British soil. That is because Britain realizes it would come off worse in tit-for-tat exchanges with Russia.

Considering defence only, it is possible to conceive of a large country with sufficient resources being able to conduct its defence with low and high powered nuclear weapons. The threat of low level nuclear contaminants landing on enemy soil would be sufficient deterrent to attackers. In the light of one comment I have removed the part of my answer about fomenting dissent because, as one commenter quite rightly noted, the key concept of defence is having graduated deterrent response to attack.

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  • Hi please check out the tour and the help center, as well as the faq. Seeing as how you just answered a question, the most relevant pieces of the help center/faq would be about answering, though if you want to do something else you might want to check other parts of the help center/faq. Note: I noticed you have looked at the tour in a different community, but I would recommend still looking at it here, as it is quite important. May 14 at 17:40
  • Now, about the content of your question, you bring up terrorist attacks, which while effective (for the reasons you detail in your question) would be difficult for a country to use as a country cannot hide very well. Thank you for contributing. May 14 at 17:42
  • Terror tactics are not that effective, because it is trivial to trace the origin of nuclear material. That's why the rest of the world is not poisoning your water with their nuclear material, hoping to blame it on incompetence in your government, fomenting dissent, and then infiltrating your country to provide leadership to the new dissidents, as well as guarantees of trade concessions if they overthrow the current govt. You can only provide a deterrent, you have no way of providing incentives. Or do you intend to nuke the protestors? What if they live in your grain fields?
    – chiggsy
    May 15 at 6:06
  • @chiggsy Your point is well taken, and I have amended my answer in light of some of what you said. However, I would suggest that my water is not being poisoned because my country has not attacked another country with the capability and willingness to poison my water. May 15 at 9:33
  • "Terror tactics" as you call them would be pretty useless against the most potentially dangerous of Japan's rivals. North Korea is probably impossible to infiltrate given that it is basically a giant military prison.
    – Joe
    May 15 at 11:03
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If the only way you have to respond to an attack is nuclear weapons then you have no options available in how you respond to an attack this leads to a number of very critical flaws in your defensive plans

If you have no conventional military forces that means you have no submarine fleet or airforce, so the only way to deploy is via ICBM. What happens if your enemy finds a way to shoot down ICBMs reliably?

How do you react to an attack that occurs within your own cities? If an enemy manages to sneak a small force into your capital and attacks your government buildings are you going to nuke your own people to stop them?

Also conventional military have other uses such as in emergency relief where having a large body of disciplined personnel with equipment and supplies ready to go at a moments notice can save lives

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