The Mainichi Shimbun answers some common questions readers may have about how widely nuclear weapons are possessed across the world as this year's Nobel Peace Prize went to Nihon Hidankyo, the grassroots organization of "hibakusha" atomic bomb survivors in Japan.

Nihon Hidankyo has been actively engaged in testimonies of A-bomb experiences in pursuit of a world without nuclear weapons. However, the global situation regarding such weapons is becoming increasingly unstable, triggered by Russia's invasion of Ukraine and North Korea's missile launches. What will happen if nuclear weapons are used? Why are nuclear weapons so horrible?

Question: How many nuclear weapons are there in the world?

Answer: The Stockholm International Peace Research Institute (SIPRI) in Sweden estimated that as of January 2024 the total number of the nuclear stockpile was 12,121.

The largest number is the 5,580 held by Russia, followed by the U.S. with 5,044. These two possess nearly 90% of the world's nuclear arsenal. The five major nuclear powers, including China with 500, France with 290 and the U.K. with 225, account for 96% of the global stockpile.

Q: Have any new countries come to possess nuclear weapons?

A: SIPRI estimates that India has 172 nuclear warheads, Pakistan 170, Israel 90, and North Korea 50, triggered by unstable relations with neighboring countries. India and Pakistan have had repeated wars with each other, and their conflict still continues. Israel has invaded the Palestinian territory of Gaza, and also clashes with other Middle Eastern nations. At odds with Japan, South Korea and the U.S., North Korea has conducted nuclear tests six times since its first one in 2006.

Q: Has the number of nuclear weapons been decreasing?

A: The number peaked in the late 1980s, at the end of the Cold War, when there were reportedly more than 70,000 nuclear warheads in the world. Following the collapse of the Soviet Union, the world has seen fewer nuclear weapons, due to the nuclear disarmament efforts by the U.S. and Russia.

In 1991, the Strategic Arms Reduction Treaty (START) was signed between the U.S. and then the Soviet Union, and over the next 10 years the number of nuclear warheads in both countries was reduced by half. These moves were motivated by changes in the international situation surrounding the U.S., such as Russia's financial difficulties and the rise of other countries. In 2010, the New START was signed, which limits the total number of nuclear warheads and means of transport, and was extended for five years in 2021.

Q: How are countries around the world working toward nuclear disarmament?

A: The Treaty on the Non-Proliferation of Nuclear Weapons (NPT) is designed to prevent the spread of nuclear arms around the world. While limiting the possession of such weapons to the U.S., Russia, the U.K., France and China, it prohibits the possession by other nations and obligates the five countries to negotiate for nuclear arms reduction.

Although the NPT's content can be seen as unfair, non-nuclear weapon states that emphasized the importance of preventing nuclear proliferation agreed to the treaty, which came into effect in 1970.

A total of 191 countries and regions have joined the treaty. Israel, India and Pakistan have not joined, and North Korea unilaterally announced its withdrawal from the treaty in 2003.

Q: What about the Treaty on the Prohibition of Nuclear Weapons?

A: This treaty, which lays out a total ban on possession and use of nuclear arms, was adopted at a negotiation conference held at the United Nations headquarters in 2017, with the support from over 60% of U.N. member states. At present, about 70 countries and regions have ratified it. The nuclear powers and Japan, which is under the "nuclear umbrella," are not signatories to the treaty, but there are growing calls for Tokyo to ratify it, especially from A-bomb survivor groups.

Q: Is there a possibility that nuclear weapons will be used?

A: The nuclear threat is increasing, such as Russia having hinted at the possibility of using nuclear arms amid its invasion of Ukraine. In addition, the U.S. has indicated that China will strengthen its nuclear capability, suggesting that countries remain divided on the issue of nuclear disarmament.

Although the number of nuclear weapons is decreasing, the more than 12,000 warheads in the world have the power to annihilate the human race many times over. It is essential that the international community make a sincere effort to determine how to move forward toward a nuclear-free world.

(Japanese original by Kana Takagi, Osaka City News Department; and Deockwoo An, Hiroshima Bureau)