After Japan surrendered to Allied forces in 1945, the Potsdam Declaration required Japanese military forces to be disarmed, limited Japanese sovereignty to specific islands, and prohibited Japanese industries from rearming the country for war (among other things).

The Treaty of San Francisco (which officially declared peace between the U.S. and Japan and ended the American occupation) recognized Japan as a sovereign nation and allowed Japan to create a security force for its own defense, but reiterated that it could not arm itself to be an offensive threat.

Both the surrender and the peace treaty are pretty vague about when and how they should expire. Here we are 70+ years later, Japan is the world's third largest economy and has the world's 11th largest population. It has been a self-governing independent nation since the 1950's. And yet, it still does not have its own military. It does have the Self-Defense Forces (SDF), which is a de facto army, navy, and air force. But officially they are only a defensive force.

The Japanese Constitution contains the declaration that:

... the Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as means of settling international disputes.

And also:

...land, sea, and air forces, as well as other war potential, will never be maintained.

However, this text was directly written by the United States after the war.

Given the recent tensions with North Korea, and China's brazen claim to pretty much the entirety of the South China Sea, can the Japanese legally build an offensive military force to counter those threats? Would they be able to fight alongside other countries if (God forbid) a war broke out with North Korea or China? In other words, are they pacifists by choice, or are they still bound by their terms of surrender and the treaties they signed?

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    "...which is a de facto army, navy, and air force. But officially they are only a defensive force." Sounds like the obvious way out, doesn't it. Also note that defense can be seen pretty pro-active. – Trilarion Aug 15 '17 at 11:46
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    the Japanese people forever renounce war as a sovereign right – hanshenrik Aug 15 '17 at 18:20
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    @Trilarion; Japan is pretty serious about the "strictly for defense" shtick though. When they sent troops to Afghanistan, they were unarmed. Japan does not carry out offensive military exercises and they don't create contingency plans that contain invasion as a course of action. Preemption is not a part of their defensive strategy at all. – Wes Sayeed Aug 15 '17 at 18:37
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    'legally' and 'bound' get less meaningful when "says you and what army?" has an answer. – user9389 Aug 15 '17 at 22:42
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    Japan does have its own military, it's number 8 in the world by military expenditure, number 18 by the number of active military personnel. It's slightly below the weight of the country (GDP and/or population) and makes a point in not participating in oversees operations but it is nonetheless very significant. The fact it's called “self-defense force” is really a detail in all this. – Relaxed Aug 16 '17 at 15:54


Pacta sunt servanda, agreements must be kept. The Treaty of San Francisco is 70 years old which is young compared to many older treaties. Agreements have a few "outs," neither of which are valid in Japan's case:

Duress: Agreements signed under duress can sometimes be nullified. Japan could perhaps be said to be under duress from the United States. As any unconditional surrender is likely at least partially due to duress. But as far as I know, the duress argument does not work at all for state parties.

Rebus sic stantibus: This is similar to the concept of force majeure. The state argues that unforeseen events have made the treaty inapplicable. However, this doctrine is seen as very limited in scope as it otherwise would make it very easy for states to escape from their obligations. Japan could perhaps argue that the nuclear armament of North Korea is such an unforeseen event.

I don't think that argument holds merit because Japan at the time of its unconditional surrender had already been bombed twice by nuclear weapons. Therefore, that a nearby power could acquire such weapons could not possibly qualify as a "fundamental change of circumstances."

Law of State Succession: If a state succeeds another, it is not necessarily bound by all treaties that the previous state signed. For example, after the 1917 Russian Revolution, the Soviet Union claimed that it was a new state, distinct from the Russian Empire, and that it therefore wasn't bound by the treaties that the previous state had signed.

Neither this out is applicable to Japan. It is clearly the same state as it was when the San Francisco treaty was signed.

So yes, Japan is bound by the treaty. But the treaty text is open to interpretation.

Constitution vs treaties

Note that the relevant article of the Potsdam declaration reads:

Japan shall be permitted to maintain such industries as will sustain her economy and permit the exaction of just reparations in kind, but not those which would enable her to rearm for war.

This is the article Japan is bound to by international law. The Japanese constitution, on the other hand, states:

Aspiring sincerely to an international peace based on justice and order, the Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as means of settling international disputes.

But articles of constitutions have no bearing on international law. They are better viewed as "treaties" between the state and the people of that state. Although it would certainly annoy their neighbors, Japan is free to do whatever it wants with its constitution as it is an entirely domestic matter.

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    "Japan is bound by the treaty" Bound legally. Of course they could just ignore it and see what happens. – Trilarion Aug 15 '17 at 11:51
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    @Random832 It would be a little difficult for the USSR to declare war on Japan these days :) – Neal Aug 15 '17 at 17:50
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    During World War II, the UK asked Portugal for basing rights in the Azores citing a 1373 treaty between England and Portugal. As far as I know, it is still in effect. Compared to that, a 70 year old treaty is indeed young. – Patricia Shanahan Aug 15 '17 at 18:38
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    @Trilarion or they could just ask the US to renegotiate. The US probably wouldn't mind another armed ally. – PyRulez Aug 15 '17 at 20:22
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    There is another way out of an agreement: all signatories could agree to dissolve it. And there's also yet another way: all of the signatories that have enough power to actually enforce the terms of the treaty in any meaningful way could simply agree to stop enforcing it and/or replace it with another treaty. – reirab Aug 15 '17 at 22:06

Is Japan still bound by the terms of its surrender in WWII?

Yes, but...

Can the Japanese legally build an offensive military force to counter those threats? In other words, are they pacifists by choice, or are they still bound by their terms of surrender and the treaties they signed?

Japan recently announced it was working on revising its constitution, following a reinterpretation of its constitution in 2014 whereby attacks against its allies would also be treated as self-defense. China and Korea protested at the time; the US backed them. (They're still pacifists, it's merely to cross t's and dot i's.)


can the Japanese legally build an offensive military force to counter those threats?

No. But it's trivially easy to build a large defensive force to protect yourself, your friends and your interests, even if it far away from your home territory.


In July 2014, Japan's government approved a reinterpretation of this article despite concerns and disapproval from mainland China and South Korea, although the United States supported the move. This reinterpretation would allow Japan to exercise the right of "collective self defense" and exercise military action if one of its allies were to be attacked. It is considered by some parties as illegitimate, posing a serious danger to Japan's democracy since the Prime Minister circumvented the constitutional amendment procedure, dictating a radical change to the meaning of fundamental principles in the Constitution by way of Cabinet fiat without Diet debate, vote, or public approval.

In May 2017, Japanese Prime Minister Abe set a 2020 deadline for revising Article 9, which would legitimize the JSDF in the Constitution.

(For example, the US has the Department of Defense and yet regularly invades other countries with the justification of defending US interests.)

  • If you are invading, you aren't exactly on the defense. Note the specifics of Japan's constitution. – user1530 Aug 15 '17 at 23:21
  • That's why I explicitly wrote "with the justification of defensing[sic] US interests." Politicians, lawyers are great at twisting words out of all definition. Not that Japan would have to invade, but building a large navy to protect their interests in, say, Brazil, is easily justifiable by someone who wants to do it. – RonJohn Aug 15 '17 at 23:30
  • Except it isn't...again, the US has a very different set of rules than Japan has...they explicitly forbid invasion. – user1530 Aug 15 '17 at 23:36
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    The US Department of War was renamed the Department of Defense in 1949 (1947 technically). I suspect the renaming was a public relations exercise rather than a fundamental shift in military strategy; since it was the same Act that created the CIA. – LateralFractal Aug 16 '17 at 7:54
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    The name of the government department that runs the military is irrelevant: it's just the name. The US government could rename it the Department of Fluffy Bunnies if it wanted to. (Preferably retroactively, so that Donald Rumsfeld would be known as the former SecFluffBun.) – David Richerby Aug 16 '17 at 14:27

That first bit is a kinda interesting if you look carefully at it...

... the Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as means of settling international disputes.

The first of those two bold sections can be interpreted as the nation's right to declare war on another country. Similarly, the second section relates to saying "do what we tell you or we'll declare war".

What it doesn't say is "we won't defend ourselves if attacked".

The second bit is the sticky bit, but the standing interpretation seems to be that there is a difference between a military force for defensive purposes and one for offensive purposes. And that is true, the infrastructure needed to engage on foreign soil is pretty specific to such things. Things like munition supply lines and landing craft aren't so important if you're fighting in and around your own country, it's unlikely you'd need to air drop troops to defend your own coast, and so on.

So, while the spirit of Article 9 stands, the interpretation is a little less clear.

It gets sticky in the second part of the question, how much can Article 9 be rewritten... to that, there's actually quite a bit of freedom. I think they'd need to retain a spirit of pacifism, but the Potsdam Declaration doesn't appear to have a requirement that it remain at all. Their surrender did dissolve the military at the time, and stipulated they were after a peacefully inclined government, but didn't actually require either case remain indefinitely.

There are other related treaties, I don't think any of them are enforcing pacifism on the grounds that they likely also don't enforce international protection of Japan, but I have to admit to having not checked too deeply on the matter. It is worth noting though that Japanese military development has been done under supervision, approval and assistance of the USA.


The Instrument of Surrender is no longer applicable after the signing of the Treaty of San Francisco, which restored sovereignty to Japan.

The Treaty of San Francisco does not state that Japan "could not arm itself to be an offensive threat." Nowhere in the treaty can I find that. In the treaty, Japan does accept the obligations of the United Nations Charter with respect to pacific settlement of disputes, but so do all the member states of the United Nations, so Japan is not any more restricted by this provision than any other UN member state is.

The constitution of Japan is an internal matter and not an international obligation, and therefore Japan is free to unilaterally change or re-interpret its constitution without any other country having standing to challenge it, as long as such a change doesn't violate any treaties it has signed.

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    This answer seems to be at odds with every other answer on this question. Not saying you're wrong, but it would probably be a good idea to add some more information/references demonstrating that your answer is in fact correct. – Martin Tournoij Sep 8 '17 at 4:43

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