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Digital Archive International History Declassified

December 12, 1966


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    The Disarmament Office at the Japanese Foreign Ministry reviews three "problematic" aspects of the NPT from the perspective of Japan's national security.
    "Disarmament Office, United Nations Bureau, Japanese Foreign Ministry, 'Regarding the Relationship between the Nuclear Non-proliferation Issue and Japan’s Security (Draft)," December 12, 1966, History and Public Policy Program Digital Archive, Diplomatic Archives of the Ministry of Foreign Affairs of Japan, File No. 2016-0117. Contributed by Yoko Iwama and Yu Takeda and translated by Ju Hyung Kim.
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Regarding the Relationship between the Nuclear Non-Proliferation Issue and Japan’s Security (Draft)


Disarmament Office, United Nations Bureau [Ministry of Foreign Affairs]      



In view of the various recent discussions surrounding the relationship between the Non-Proliferation Treaty and Japan’s national security, here is our tentative perspective on this point. Of course, the Nuclear Non-Proliferation Treaty has not yet been concluded as of now, and it is difficult to say for sure how it will affect Japan’s security unless the contents of the Treaty are fixed. However, this report examines possible impacts of three problematic points on Japan’s national security: the prohibition of the “manufacture” and “acquisition” of nuclear weapons, the prohibition of the “introduction” of nuclear weapons, and the prohibition of the “consultation” on issues such as nuclear strategy. It concludes that while Japan needs to make efforts for the time being to ensure that this Treaty does not impair the functioning of the Japan-U.S. security arrangements, the possibility of such harm is small in light of the previous talks. Any comments are welcome.

1. Prohibition of “manufacture” and “acquisition” of nuclear weapons and Japan’s national security

(1) Prohibiting non-nuclear weapons states from “manufacturing” or “acquiring” nuclear weapons is the original purpose of the Treaty. Thus, the above two prohibitions will certainly be included in the Treaty, regardless of its concerns.

(2) (a) Whether you saw an impact of the above two prohibitions on Japan’s national security depends on whether you think Japan should possess its own nuclear forces in the future. If you think Japan needs to do so, the above two prohibitions would impose the most intolerable security constraints on Japan.

(b) There could be various types of claims that Japan should possess its own nuclear forces. The most typical of which is a kind of theory of Gallois[1] , which is summarized as follows:

(i) Sooner or later, the People’s Republic of China will built their nuclear arsenal and possess enough nuclear weapons to directly hit the U.S. mainland. In this case, the U.S. nuclear deterrence will be checked by Chinese nuclear forces. If China were to attack Japan, the U.S. might not be able to deter China. Therefore Japan needs to maintain its own nuclear deterrence against China.

(ii) If Japan is to have its own nuclear deterrent against China, it must be invulnerable. But it does not need to be sufficient to destruct the entire territory of China. It should be sufficient if it can cause enough damage to offset the benefit that China would gain by attacking Japan. It is because nuclear deterrence is a force that is sufficient to dissuade the other party from initiating an attack in advance.

(c) The above claims may not be unreasonable. Considering the progress of China's nuclear development, it is only a matter of time before China acquires nuclear forces that could reach to the United States (the timing is said to be around 1975). Furthermore, if the United States does not maintain its current superiority in the development and deployment of anti-missile missiles, Japan's security position may be weakened. However, it is natural to expect that the United States will make every effort to secure deterrence against China. There is no need for Japan to possess its own nuclear forces even if such efforts by the United States will result in failure at this stage. Moreover, taking such steps means to express distrust of the U.S. deterrent capability, which would undermine the effectiveness of the security treaty on our fault. In any case, Japan declared not to go nuclear in its policy and the principle of the Atomic Energy Basic Law, Even if the Nuclear Non-Proliferation Treaty prohibits the “manufacture” and “acquisition” of nuclear weapons, it cannot be said that it will cause damage to our national security. (Nonetheless, we cannot conclude that there is no need to change such policies in the future. From this point of view, it is vital to stipulate that the Nuclear Non-Proliferation Treaty is valid for a limited period of time.)

(3) With regard to “acquisition,” if Japan were to acquire nuclear weapons from another country, in the present situation, it is only possible to acquire them from the United States. However, if that country joins the Nuclear Non-Proliferation Treaty, the transfer of nuclear weapons would be prohibited. Therefore there would be no way for Japan to acquire them, regardless of whether Japan joins the Treaty or not. Consequently, the way to an acquisition of nuclear weapons is closed by the establishment of this Treaty and has no direct connection with Japan’s participation to the Treaty. As for “manufacture,” Japan, as a party to the 1963 Partial Nuclear Test Ban Treaty, was prohibited from conducting all nuclear tests except those held in underground. Japan is already under significant restrictions on “manufacturing” nuclear weapons in this respect.


2. Prohibition of the “introduction” of nuclear weapons and Japan's security

(1) In addition to prohibiting the “manufacture” and “acquisition” of nuclear weapons, in relations to Japan’s national security, whether the Nuclear Non-Proliferation Treaty prohibits the so-called “introduction” could be problematic (the introduction means physical deployment of a nuclear weapon within foreign territory. It differs from “acquisition” in that the right to control the firing and other activities of the weapon is in the hands of the country in which the weapon is deployed).

Though Japan declared a policy not to tolerate the “introduction” of nuclear weapons into the country, in fact it is legally possible that U.S. nuclear weapons are “introduced” into Japan, on the condition that it is approved by prior consultations under Article 6 of the Japan-U.S. Security Treaty and the exchange of notes. Practically speaking, considering China, it should also be anticipated that Japan may need to “introduce” nuclear weapons of a defensive nature. From this perspective, it is clear that if the Nuclear Non-Proliferation Treaty were to prohibit even the “introduction” of nuclear weapons, it would result in the “corrosion” of the Security Treaty in that part. Japan’s security would suffer a negative impact.

(2) However, considering previous consultations and negotiations regarding the Nuclear Non-Proliferation Treaty, it is unlikely that the Nuclear Non-Proliferation Treaty will be prohibiting even the “introduction” of nuclear weapons. In fact, the United States is thought to have deployed tactical nuclear weapons within NATO countries such as West Germany. While there is no evidence that the Soviet Union has not deployed nuclear weapons in Eastern Europe, in the previous negotiating process, the Soviet Union has not raised issues regarding the prohibition of the “introduction” of nuclear weapons. (Nevertheless, at this year’s Eighteen Nation Committee on Disarmament (ENDC), some Eastern European countries insisted that the introduction of weapons should be prohibited. In addition, the so-called “Kosygin Proposal” can be said to made it difficult to introduce nuclear weapons in an indirect manner). Even if the Soviet Union or other countries make a official proposal to prohibit the “introduction” of nuclear weapons, the United States is unlikely to accept such a proposal in light of its commitment to the defense of Western Europe.

(3) Of course, whether the “introduction” is prohibited under the Nuclear Non-Proliferation Treaty will be determined after the Treaty is established. It goes without saying that all possibilities should be taken into consideration since the negotiation is still underway. If such prohibition were to be imposed, it would have significant impact on Japan's security. Therefore it would be necessary to take measures such as  requesting the United States not to prohibit the “introduction” in the treat at some point.

3. Prohibition of “consultations” on issues such as nuclear strategy and Japan's security

(1) Consultations on issues such as nuclear strategy refer to discussions on issues including the formulation of nuclear programs, the selection of targets, the use of nuclear weapons as deterrence in the peacetime. Given that Japan’s security is basically depend on U.S. nuclear deterrence in accordance with the Japan-U.S. Security Treaty, it is likely that this kind of consultation with the United States will be necessary in the future. If the Nuclear Non-Proliferation Treaty prohibits it, it will have substantial impact on Japan’s security.

(2) However, as mentioned above, the Nuclear Non-Proliferation Treaty is currently under negotiation and it is unlikely that the Nuclear Non-Proliferation Treaty will prohibit such “consultations” in light of the previous negotiations. In fact, the United States has consistently rejected the Soviet Union’s claim that holding this kind of consultation within NATO is also nuclear proliferation. Recently, the Soviet Union reportedly has taken an attitude of not objecting to arrangements such as the so-called McNamara Committee (an organization within NATO for discussing the formulation of a nuclear program, the selection of targets, the use of nuclear weapons, etc. Although it was established as a provisional organization, the proposal to make it a permanent organization was adopted at the nuclear working group at the end of September this year. The proposal is set to be discussed at the NATO Ministerial Council in December).

(3) It is unlikely that such “consultations” will be prohibited under the Nuclear Non-Proliferation Treaty. Needless to say, it is necessary to pay close attention to subsequent negotiations between the United States and the Soviet Union, and to back up the U.S. position against the prohibition.

As a side note, it goes without saying that it is unnecessary to explicitly stipulate that “consultations” can be held in the Nuclear Non-Proliferation Treaty. It would be enough for our country if the consultations were not prohibited. As long as such “consultations” are not prohibited, the extent to which such consultations are actually conducted is a matter to be solved in relation to the Japan-U.S. security arrangements.

4. Conclusion

As is discussed in the above, the prohibition of “manufacture” and “acquisition” under the Nuclear Non-Proliferation Treaty will not affect Japan's national security at least for the time being. Therefore it is sufficient for Japan to be cautious that the prohibition of “introduction” and the prohibition of “consultation” on nuclear strategic issues will not be realized henceforth. In other words, it is sufficient to pay attention that the Nuclear Non-Proliferation Treaty does not harm every functions of the Japan-U.S. Security Arrangements. This point has already been expressed by Japan at the UN General Assembly of [sic] the UN Disarmament Commission (UNDC) and other meetings. Incidentally, among the views expressed by Ambassador Matsui at the UN General Assembly on nuclear non-proliferation issues, the following is a summary of the sentences that refer to the security of non-nuclear weapons states.

“The biggest obstacle that hindered the progress of the discussion on nuclear non-proliferation issues at the Eighteen Nation Committee on Disarmament this year is that the word “nuclear proliferation” was interpreted in various ways. We hope that opinions on this point will be unified as soon as possible. However, we believe that the broad understanding of the meaning of this term should not prevent non-nuclear weapons states from taking measures that they think necessary for their national security against nuclear attacks or threats, without acquiring nuclear weapons, through bilateral or multilateral arrangements.”

[1] The theory was named after French nuclear strategist Pierre Marie Gallois.


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