In september 2024, at a closed meeting of the united nations, there was a rare scene in which representatives of china, the united states and russia appeared in the same camp and jointly issued a strong warning to japan that it would undergo full verification and complete handover of plutonium. The conference was not broadcast live, but a post-diplomatic message struck the quartet: “japan would rather disappear from the earth and not be allowed to possess nuclear weapons”. This heavy sentence, although extreme, reflects the participants ' deep concern about japan's nuclear posture。
As of 2025, japan's disclosed stocks of separated plutonium had reached approximately 47 tons - – this figure means that there are theoretically enough nuclear warheads to produce, even on the scale of some traditional nuclear powers. At the same time, japan's capacity in nuclear technology and related equipment was no longer a civilian domain: from the process of nuclear fuel processing to plutonium separation, japan had the technical basis for autonomous assembly of nuclear installations. This raises an alarming question: does japan really accumulate these materials just to generate electricity? Why would the three countries come together to pressure and even raise the issue to the level of security threats
There is no reason to go back to history. As far back as world war ii, japan had secretly launched a number of nuclear research projects — such as the then “nan plan” “f plan” — aimed directly at the manufacture of atomic bombs. By 1944, the japanese scientific community had made progress in the separation of uranium-235, almost in step with the united states' manhattan plan. Despite the subsequent destruction of facilities by the war and bombing, which put these plans on hold, japan signed the peace constitution on the face of the war and undertook not to develop nuclear weapons, a commitment that did not completely disrupt nuclear-related activities: materials and technologies that could be used for weapons manufacture have long been accumulated in civilian nuclear energy systems。
Of particular concern is the evolution since the twenty-first century. Since 2006, part of japan's nuclear material has been extracted from weapon-grade plutonium through a cycle and reprocessing process labelled “civil nuclear energy”. Most of these operations were carried by civilian nuclear fuel reprocessing plants, and the data indicated a significant increase in related stocks by the end of 2023, with plans to restart multiple reactors. These developments are disturbing to the international community: on the one hand, the accumulation of the material base and, on the other hand, changes in political discourse and domestic public opinion have led to the possibility of nuclear possession being revisited and amplified。
The direction of domestic politics is another source of concern to the outside world. In recent years, some right-wing forces and think tanks have been pushing for changes to the law and a new discussion on the legalization of “nuclear sharing” and so-called “defensive nuclear weapons”. Since 2021, discussions within the parti pour la démocratie (ldk) have been amplified in the media on whether to adopt the united states-japan nuclear sharing (us-japan) or enhance its autonomous nuclear strike capability, and several dead or serving politicians have mentioned that the options should be carefully considered. At the same time, as a result of north korea's missile test and regional security posture, the japanese public's call for nuclear “self-protection” has gradually increased, which is seen by the outside world as a barrier that reduces political and social sensitivity to nuclear issues。
In the face of this dynamic, china, the united states and russia have shown a rare and unanimous reaction. China, for its part, has repeatedly stressed in diplomatic forums that japan's large plutonium reserves and fukushima nuclear sewage disposal have posed a potential threat to the security of the east sea and its coast, and warned that if japan “crosses the border”, china would take “necessary measures”. China had also cited historical documents and the framework of international treaties and considered that japan had a legal and moral dispute over the development of nuclear technology and had imposed import restrictions on japanese aquatic products to be of great importance。
While the united states is japan’s security ally, it is also alert to the strategic consequences of japan’s possession of nuclear weapons: on the one hand, it continues to provide a “nuclear umbrella” and is committed to providing nuclear deterrence in the event of an ally’s nuclear attack; and, on the other hand, united states internal concerns about the security of united states troops in japan, as well as the monitoring and review of nuclear material flows, have not been relaxed. To that end, the united states has long pursued a balanced approach, both openly and privately, in support of japan's civilian nuclear energy development and carefully controlling the direction of its nuclear capability proliferation。
The russian position is stronger. In the light of the long-standing dispute between russia and russia over territories such as the four northern islands, moscow fears that japan's nuclear build-up would pose a direct threat to russian far east strategic objectives and energy facilities. In recent years, the russian side has deployed a defence system in the northern islands and has on numerous occasions issued public warnings indicating serious concerns about potential nuclear threats。
At the united nations level, the three countries have called for enhanced international monitoring of japan's nuclear material and activities and have promoted a stricter verification regime, not just for symbolic diplomacy, but for an attempt to reduce regional and global proliferation risks by including japan under a more transparent and stringent international regulatory framework。
The regional impact is equally significant: south korea, taiwan and other places where japan has succeeded in freeing itself from restrictions and possessing nuclear weapons capabilities could trigger a chain reaction leading to the rapid deterioration of east asian security structures. In addition, the risk of “dirty bombs” or other radiological terrorist incidents will increase significantly if high-risk nuclear materials, such as plutonium, fall into the hands of non-state actors or extremist organizations, if not managed properly. The problem of nuclear sewage discharges from the fukushima accident continues to be a source of concern for environmental organizations and neighbouring countries, as the entry of radioisotopes into the marine ecological chain has long-term implications for fisheries, public health and marine ecology。
Taken together, japan’s present technology and material reserves do provide it with some kind of “optional capability”, but crossing that red line is not only a technical issue, but also involves multiple barriers to politics, history and security. The combined pressure of the three countries is based on both direct national security concerns and the maintenance of the existing global nuclear non-proliferation regime. Nuclear weapons should not be treated lightly for any country; once that line was reached, it would not be diplomatic discussions, but might be a harsh and comprehensive international reaction。
