【By Observer Net Columnist Chen Feng】
When Japanese Prime Minister Takahashi Hayato made a speech in the Japanese Diet, she hinted that the Japanese government may adjust the long-standing "Three Non-Nuclear Principles," which are not to possess, not to manufacture, and not to introduce nuclear weapons. When answering questions from opposition party members, Takahashi said, "I cannot make a clear statement now, nor can I assert how the document will be phrased (on the Three Non-Nuclear Principles)." However, she added that the current Japanese government still regards the "Three Non-Nuclear Principles" as a policy guideline.
Takahashi's past statements and her ambiguous attitude toward the "Three Non-Nuclear Principles" have led to speculation that she may intend to revise the third principle, "not introducing nuclear weapons," where "introducing" refers to foreign nuclear weapons being deployed in Japan, not the introduction of manufacturing. In 2024, Takahashi wrote in her book that this principle "is not realistic" because "the US may need to deploy nuclear weapons in Japan to deter opponents."
According to Japan's Kyodo News, Japanese Defense Minister Koizumi Shinjiro mentioned the necessity of introducing (here referring to Japan's own design and manufacture) nuclear-powered submarines on TBS on November 6, saying, "The security environment Japan is in has become so severe that it must seriously discuss whether the Self-Defense Forces' submarines should use diesel or nuclear power."
On November 14, Chinese Foreign Ministry spokesperson Lin Jian expressed serious concerns about Japan's recent military and security moves at a regular press conference. The significant negative shift in Japan's policies is sending out a dangerous signal to the international community.
Japanese Defense Minister Koizumi Shinjiro mentioned the necessity of introducing nuclear-powered submarines on TBS on November 6
After the war, Japan has generally adhered to the "Three Non-Nuclear Principles," first formally proposed by former Prime Minister Sato Eisaku in a speech in the Diet in December 1967 and further supplemented in his State of the Nation address in January 1968, becoming the "four pillars" of nuclear policy, namely, nuclear abstinence, nuclear disarmament, reliance on U.S. nuclear deterrence, and the peaceful use of nuclear energy. In November 1971, the Japanese House of Representatives approved the "Three Non-Nuclear Principles," making them the basic policy of the Japanese government regarding nuclear weapons. Sato was awarded the 1974 Nobel Peace Prize for advocating the "Three Non-Nuclear Principles."
But Japan's proposal of the "Three Non-Nuclear Principles" was more about the Japanese government trying to tie down the U.S. nuclear umbrella than due to public anti-nuclear sentiment in Japan.
On December 22, 2008, major Japanese media reported that according to newly declassified diplomatic documents from the Ministry of Foreign Affairs, in a meeting with then-U.S. Secretary of Defense McNamara on January 13, 1965, Sato requested that the United States launch a preemptive nuclear attack on China if war broke out between China and Japan. In the conversation, Sato also expressed a default attitude towards the issue of nuclear weapon introduction, contradicting his later publicly stated position of the "Three Non-Nuclear Principles."
The meeting between Sato and McNamara took place shortly after China's first successful nuclear test. McNamara asked, "How will the situation develop in the next two or three years? Does Japan have any plans for nuclear development?" Sato replied, "Japan will always oppose having and using nuclear weapons," reiterating his desire to remain under the U.S. nuclear umbrella. At the same time, he emphasized, "Regarding the issue of introducing nuclear weapons, it is stipulated in the Security Treaty, so we should be cautious when speaking about land-based introduction. ... If (a war) occurs with China, we expect the U.S. to retaliate with nuclear weapons immediately. At that time, although building land-based nuclear facilities is not simple, if it is at sea, we can start immediately." To this, McNamara replied, "There are no technical problems."
In 1998, the U.S. declassified documents confirmed this conversation and also revealed that Sato had once said, "If China has nuclear weapons, Japan should consider having them too," but this statement was not included in the publicly released Japanese declassified documents in 2008. However, Sato told McNamara, "Of course, technically, we can produce nuclear bombs. ... We are producing propulsion devices for space development, which can be converted for military use if necessary." In other words, Sato informed the U.S. that Japan has the capability to manufacture nuclear weapons but does not intend to materialize it, instead relying on the U.S. nuclear umbrella.
For many years, even at the official level, Japan has maintained an ambiguous stance on the "Three Non-Nuclear Principles," especially regarding the issue of U.S. aircraft carriers entering Japanese ports. If there is a dispute over whether nuclear power counts as "nuclear introduction," the fact that U.S. aircraft carriers carry nuclear weapons is undeniably "nuclear introduction."
American nuclear forces are divided into strategic and tactical levels. On the strategic level, the nuclear triad consisting of intercontinental missiles, strategic bombers, and ballistic missile submarines is well known; however, there was also a tactical nuclear triad. After the end of the Cold War, medium-range missiles and land-based cruise missiles were withdrawn, leaving the Army's tactical nuclear force absent. But after the re-introduction of medium-range missiles and land-based cruise missiles, the Army's tactical nuclear force has returned.
The Air Force has always retained the option of dropping nuclear bombs from strategic bombers. To avoid accidental activation of nuclear upgrades during the use of "Tomahawk" cruise missiles, the U.S. removed "nuclear Tomahawks" and fully converted the "Tomahawk" to conventional use, concentrating its naval tactical nuclear force on aircraft capable of dropping nuclear bombs, with aircraft carriers serving as storage facilities for these naval tactical nuclear forces.
However, the U.S. policy is never to confirm or deny whether specific aircraft carriers carry nuclear weapons while on deployment. This is reasonable militarily, similar to the secrecy surrounding whether specific airbases store nuclear weapons and how many, which is considered operational deployment information.
This conflicts with the policy of refusing "nuclear introduction." New Zealand has a similar "Three Non-Nuclear Principles" because the U.S. refuses to confirm whether specific aircraft carriers carry nuclear weapons, thus refusing U.S. aircraft carriers from entering its ports. Japan has long walked the line. The "Heron" carrier has long been based in Yokosuka, and the conventional power is indeed a factor; however, Japan has always ignored the question of whether U.S. aircraft carriers (regardless of whether they are nuclear-powered) might carry nuclear weapons.
Now, Japan may break the "Three Non-Nuclear Principles" and the "Four Pillars" in two aspects:
1. Introducing U.S. nuclear weapons, breaking the "non-introduction" principle of the "Three Non-Nuclear Principles";
2. Developing nuclear-powered submarines, breaking the principle of the "Four Pillars" that nuclear energy is used only for peaceful purposes.
The balance of military forces in the Western Pacific is vastly different from before. During the 1996 Taiwan Strait missile crisis, the U.S. Navy sent two aircraft carriers to "enter the Taiwan Strait," but that is no longer the case now. The balance of military forces is no longer balanced, and tactical nuclear forces have once again become the weights to balance the scales. Not only at sea, but on land as well, it is equally important.
The U.S. Army has renewed its focus on medium-range missiles. The ATACM launched by the "Himars" has a range of 300 kilometers, while the newly developed PrSM has a range of 500 kilometers, and future developments could reach 1,000 kilometers. However, this is still below the threshold of usefulness for the vast Western Pacific.
The Mk41 vertical launch system on the sea has become the "Typhon," but the modified SM6 air defense missile as a ballistic missile is not effective, and the "Tomahawk" cruise missile has become outdated. It is necessary to accelerate the development of new missiles, including the long-rumored but yet-to-be-seen hypersonic missiles.
On September 15, 2025, the U.S. publicly displayed the "Typhon" intermediate-range missile system deployed in Japan for the first time. Reuters
The problem is that for U.S. medium-range missiles to reach Chinese targets, they must be deployed in neighboring countries. The Philippines and Japan are the preferred locations for medium-range missiles. "Typhon" has indeed been deployed at the Marine Corps Air Station in Iwakuni. These missiles are all aimed at China and are capable of carrying nuclear warheads. Or rather, converting them to carry nuclear warheads is technically very simple.
China's medium-range missiles are dual-use, capable of both nuclear and conventional operations. There is nothing wrong with the U.S. medium-range missiles being dual-use, although there have been no reports of actual nuclear warhead deployment. Deploying American medium-range missiles that could carry nuclear warheads in Japan is different from the temporary and transitional nature of aircraft carriers entering Japanese ports. It crosses the threshold of "nuclear introduction" in policy, which is a serious escalation.
China's nuclear policy is not to use nuclear weapons first and not to use them against non-nuclear countries or regions. Once U.S. nuclear weapons are stationed in Japan, Japan ceases to be a non-nuclear country or region.
The principle of not using nuclear weapons first remains, but this is U.S. nuclear weapons. If the U.S. uses nuclear weapons first in other battlefields or threatens to do so, China may not mechanically apply the principle of not using nuclear weapons first because the U.S. nuclear weapons are launched from within Japan, and nuclear retaliation against Japanese targets is entirely within consideration, including domestic targets with nuclear capabilities and other strategically significant targets.
In other words, the stationing of U.S. nuclear weapons in Japan brings not only nuclear deterrence but also nuclear entanglement to Japan. Japan needs to think carefully.
The purpose of Japan developing nuclear-powered submarines is not only to counter China, but also to avoid falling behind when South Korea and Australia gain nuclear-powered submarines. But for China, it is the same: Japan is intent on developing nuclear-powered submarines.
Nuclear-powered submarines do not equal nuclear weapons, but they are "nuclear-related weapons."
"Nuclear-related" does not equal weapons. Nuclear power plants, industrial and medical radioactive equipment are non-military nuclear facilities. However, nuclear-powered submarines are military offensive weapons, a completely different nature.
Nuclear-powered submarines are the "privilege" of nuclear states. Apart from the five permanent members of the UN Security Council, India also has independently developed nuclear-powered submarines. The club of nuclear-powered submarines is expanding to South Korea and Australia, but their technological routes are completely different.
Australia has neither submarine technology nor nuclear technology, but because of its familial ties with the U.S. and the U.K., and its strategic location in the South Pacific, it was brought into AUKUS and can share nuclear-powered submarine technology with the U.S. and the U.K. AUKUS started with second-hand "Virginia"-class submarines, eventually shifting to SSN-AUKUS. This will be a completely new design led by the U.K., incorporating U.S. fire control and weapon technologies, and integrating Australian requirements and technological foundations, representing the highest level of Western technology outside the U.S. If it does not reach the one-ton level of the "Virginia"-class Block V, it should at least reach 8,000 tons, making it a "full-strength" nuclear-powered submarine.
But for Australia, this is an unbearable burden. On one hand, the exorbitant cost of nuclear submarines would crowd out Australia's limited military budget, and on the other hand, its fragile defense industry would find it impossible to bear the揠苗助长 (overstimulation). In the 1980s and 1990s, when Australia introduced the "Collins"-class submarines and the "Anzac"-class frigates, it had the intention of establishing an advanced shipbuilding industry. Thirty years later, it is still repeating the importation, and after SSN-AUKUS, it is likely to pass without leaving a trace.
South Korea, on the other hand, takes a completely different technological route. South Korea's submarine technology began with the introduction of the German 209 and 214 classes, and it has developed its own 4,000-ton "Ahn Chang-ho" class, and is confident in expanding to 5,000 tons needed for nuclear-powered submarines. South Korea has also independently developed small modular reactor (SMR) technology, and is confident in applying it to nuclear-powered submarines. What it needs from the U.S. is enriched uranium as nuclear fuel.
In July 2023, the U.S. nuclear-powered submarine "Annapolis" arrived at the Jeju Island Naval Base in South Korea. Reuters
France is the only country in the world that designs and builds 5,000-ton nuclear-powered submarines. However, the main role of French nuclear-powered attack submarines is to demonstrate presence, not combat effectiveness, so it is sufficient. South Korea may have the same considerations.
The characteristics of SMRs lie in being "small and safe." Achieving maximum power in the smallest volume is not their strength, so South Korean nuclear-powered submarines may not aim for maximum combat effectiveness from the beginning, but rather for tracking North Korean ballistic missile submarines continuously, perhaps this performance is enough.
If Japan develops nuclear-powered submarines, the technological route is still unclear. Japan has advanced conventional submarine technology and has long adopted the teardrop-shaped design commonly used in nuclear-powered submarines. Due to the emphasis on oceanic combat capabilities, Japanese submarines have long adopted large-tonnage designs. The latest "Oyashio" class exceeds 4,000 tons. Japan also has a nuclear power base, and developing reactor technology for submarines is not starting from scratch.
The key issue is what to use them for?
The usefulness of nuclear-powered submarines lies in their offensive nature. AUKUS nuclear submarines are insufficient in number, which is not very useful for defending Australia's coastline, and their usefulness lies in supplementing the U.S. nuclear-powered submarine forces in the Western Pacific to threaten China's coastline. Japan also faces the same problem.
The Japanese Maritime Self-Defense Force has many submarines, but compared to Western standards, their service life is shorter. The "Oyashio" class has been in service for over 20 years and has already begun to retire. The current mainstay is 12 "Soryu" class and ultimately 8 "Oyashio" class (five have been launched). If they want to counter China's navy, these submarines are not enough, and converting them all to nuclear-powered would be unaffordable, also crowding out Japan's military modernization and daily operations, with nuclear submarines being money guzzlers. The pressure on the Air Self-Defense Force is actually greater than the Maritime Self-Defense Force, and replacing F-35s is not useful, and the next-generation fighter jet in cooperation with the UK is still a pie in the sky, but when it finally lands, it will definitely be expensive.
The Japanese Maritime Self-Defense Force's "Oyashio" submarine (left) and "Oyashio" class submarine (right). April 2022, at the U.S. Navy's Yokosuka Base in Kanagawa Prefecture. Nippon.com
Nuclear-powered submarines are single players in the structure of naval forces, but to play a role, they actually need system support. Nuclear-powered submarines have unlimited diving capabilities, but their onboard sonar has limited detection range and resolution. A nuclear-powered submarine operating independently is like a football player who is highly nearsighted and doesn't wear glasses, unaware of where the ball is, and the ability to control the ball on the ground is pure coincidence.
The command and control of submarines is also unique. Extremely long waves are used to "awaken" submerged nuclear-powered submarines, with extremely brief messages sufficient to transmit the most general combat instructions; after surfacing to snorkel depth, satellite communication can transmit more detailed commands in bursts.
This support system can only be possessed by major powers. As an extension of the U.S. system, Australia naturally falls under the U.S. system. For South Korea, primarily targeting the East Sea, the problem is not big. Japan's situation is more delicate. On one hand, the Maritime Self-Defense Force has always emphasized joint operations with the U.S. Navy; on the other hand, Japan's need for nuclear-powered submarines itself began when the U.S. withdrew from the first island chain.
After withdrawing, how much serious command and support can the U.S. provide, and how much trust does Japan have in the command and support of an independent U.S., is something worth considering.
The most important thing is that as "nuclear-related weapons," if Japanese nuclear-powered submarines fire weapons, even conventional torpedoes, they may be interpreted as "first use of nuclear-related weapons," potentially constituting at least nuclear-related conditions for retaliation, such as all facilities related to nuclear-powered submarines, all nuclear-capable combat forces, etc.
Directly constituting conditions for nuclear retaliation is possible. Ultimately, the definition and interpretation rights of "first use of nuclear weapons" belong to China, not any other country.
Since Japan can "redefine" its nuclear policy, China can too.
China's military modernization is entering a fast lane. The visible part is the conventional military force, while the nuclear military force part is not high-profile. Western media has been wildly talking about "wind farms," but Western governments have not criticized it loudly, and Western people are also happy to ignore it.
China has long adhered to the "minimum nuclear deterrence" principle. This is a "nuclear shrimp" strategy, using "sufficient damage" as a deterrent, which historically greatly increased the threshold for superpowers to launch a nuclear strike against China.
But China has risen, "shrimp" has grown into a dragon. With the rise of Sino-American confrontation as the main security concern, only ensuring mutual destruction is sufficient deterrence. Sino-American nuclear parity has become a necessity. "Nuclear shrimp" is no longer enough.
This means that when China reaches nuclear parity with the U.S., whether Japan gives up the "Three Non-Nuclear Principles" is irrelevant to China, but for Japan, it is a matter of survival.
The world is currently in a once-in-a-century great transformation, with the biggest variable being China's rise, which is a turning point for Japan. Since the Meiji Restoration and joining Europe, Japan became the first country outside Europe to complete modernization, and has long been the "leader" in the post-war Asia-Pacific.
But China's rapid rise suddenly made Japan lose its way. In fact, the West is also experiencing changes, but Japan is different from the West. The U.S. has the option of retreating and isolating itself, and Europe has the option of choosing sides and following the wind, but Japan only has the option of becoming a second-rate country. Going west and joining the West (later, going west and joining the U.S.) means "below the West, above all nations," which has become deeply rooted in the Japanese national consciousness. The defeat in World War II, in a certain sense, reinforced rather than broke this consciousness.
Japan has no psychological obstacles in following Britain, and it's fine to follow Germany. Then, following the U.S. is essentially a matter of whether the god in the temple is on the left or the right. But "falling into the category of second-rate countries in the Asia-Pacific" is not just an economic and technological issue, but a fundamental challenge to the national consciousness.
In the Japanese national psyche, the path of rising involves hardship and effort, and expansion and colonization on the blood of neighbors is history, which is what "normal countries" do. Japan's defeat was due to not recognizing the strength of the U.S. when challenging the "top of the world," and the victory of the Chinese people's resistance is merely "riding the wave." In Japan's narrative, World War II is not World War II, but only the "China Incident" and the "Pacific War," the former was a continuous success, and the latter was from failure to greater failure, until final defeat.
Clearing up history means negating oneself, which is difficult to accept. If the U.S. withdraws from the first island chain, Japan can only stand on its own to become great again. The "Peace Constitution" is the bitter fruit of Japan's defeat, and only by (even partially) negating the "Peace Constitution" and returning to a "normal country" can Japan return to greatness. In this process, Taiwan has a special significance, which is the peak of Japan's expansion era and a key point in geopolitical and maritime trade. "Keeping Taiwan" and "returning to normal" are crucial for Japan's return to greatness. This is what Abe and Takahashi are trying to push, but it is futile.
China's rise is unstoppable, and ending the humiliation history is the foundation of the rise, and the return of Taiwan is the last chapter of ending a century of humiliation. No one, no force can block it. The U.S. cannot block it, nor can Japan. As someone said: anyone who sticks their dirty head into places where it shouldn't be, should be cut off.
China is a responsible major country, and China is taking the path of peaceful rise. If Japan is willing to be a companion of China on the path of peace and development, China is welcome; if Japan wants to be a blocker on the path of peace and development by abandoning the "Three Non-Nuclear Principles," China is also ready to crush it.
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