Tokyo Report | Politics | Security | East Asia

Whither Japan’s Three Non-Nuclear Principles?

A highly contentious debate is in the offing.

The U.S. Navy ballistic missile submarine USS Pennsylvania (SSBN 735) travels through the Hood Canal as it returns home following a strategic deterrence patrol Oct. 16, 2014, in Puget Sound, Wash.

Debate over the three non-nuclear principles has resurfaced in Japan as the government of Prime Minister Takaichi Sanae prepares a new National Security Strategy, due at the end of 2026. Even the status of the principles is contested. Some regard them as the country’s foundational principle (kokuze), while others describe them as a policy guideline, suggesting that the government is free to change it. Prime Minister Sato Eisaku first announced the principles in 1967, and the Diet has reaffirmed them on multiple occasions since then.

The principles state that Japan will neither possess nor produce nuclear weapons, nor permit their introduction into its territory. As long as Japan remains a party to the Non-Proliferation Treaty (NPT), the only practical debate concerns the third principle: non-introduction. The commitments not to possess or produce nuclear weapons nevertheless sent an important message to the world when the principles were first articulated, before Japan ratified the NPT.

In March 2010, Foreign Minister Okada Katsuya revealed that a secret agreement (mitsuyaku), broadly defined, had existed between Washington and Tokyo over the introduction of nuclear weapons. Under the U.S. interpretation, “introduction” referred only to the permanent deployment of nuclear warheads in storage facilities ashore. The Japanese government, by contrast, regarded transit through Japan’s territorial waters or port calls by nuclear-armed vessels as introduction as well. Successive Japanese leaders maintained that, in the absence of a U.S. request for “prior consultation” under the arrangements associated with the U.S.-Japan Security Treaty of 1960, Tokyo assumed that visiting U.S. vessels were not carrying nuclear weapons. Yet such vessels could not simply leave their nuclear weapons elsewhere before entering Japan. It is now an open secret that, under the Japanese definition, the United States “introduced” nuclear weapons into Japan during the Cold War.

Since the revelation in March 2010, Tokyo has maintained that there is no need to be concerned about introduction because the United States does not deploy nuclear weapons on surface vessels and has no nuclear weapon system for the vessels that regularly visit Japan. At the same time, successive Japanese governments have upheld the position Okada first articulated in the Diet that month: in extreme circumstances in which Japan’s survival cannot be secured without allowing the introduction of nuclear weapons, the government of the day “shall make a decision by taking full responsibility.” This........

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