Nuclear-armed states

A country possessing nuclear weapons; effectively nine states are discussed, including the five NPT-recognized states and unofficial possessors.

Nuclear-armed states

Overview

A nuclear-armed state (核保有國) is a country that has actually developed and possesses nuclear weapons and has the capability and will to use them when it deems necessary. There is no unified definition under international law, but in general, the five permanent members recognized by the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) as official nuclear-weapon states (the United States, Russia, the United Kingdom, France, and China) plus India, Pakistan, Israel, and North Korea, which acquired nuclear weapons outside the NPT regime, are combined to classify effectively nine countries as nuclear-armed states. Whether a state possesses nuclear weapons is not merely a matter of technical capability but functions as a key variable in the international security order and diplomatic negotiations.

Main content

Definition and criteria

There are generally three criteria for identifying a nuclear-armed state. First, does it possess nuclear weapons themselves in a form deployable for combat. Second, has it secured delivery means such as missiles, strategic bombers, and submarines to have actual operational capability. Third, does it have the political will to use nuclear weapons and an independent control system. In some cases, such as Israel, which adopts a so-called policy of ambiguity neither officially confirming nor denying nuclear possession, the question of possession itself becomes an issue in international politics. On the other hand, countries with the potential capability to nuclear-arm in a short time, such as Japan and Germany, are classified as threshold states.

Official nuclear-weapon states under the NPT regime (P5)

The NPT, opened for signature in 1968 and entered into force in 1970, distinguishes in Articles I and II the obligations of nuclear-weapon states and non-nuclear-weapon states. The nuclear-weapon states defined by the treaty are limited to states that manufactured and exploded a nuclear weapon or other nuclear explosive device before January 1, 1967, namely the United States, the Soviet Union (with Russia succeeding to its status), the United Kingdom, France, and China. These five states, combined with their status as permanent members of the United Nations Security Council, have formed the central axis of the nuclear order. However, the prevailing interpretation is that the NPT did not permanently legalize their possession of nuclear weapons, but rather was a provisional recognition requiring them ultimately to implement nuclear disarmament.

De facto nuclear-armed states outside the NPT

India conducted a peaceful nuclear explosion test in 1974 and a series of nuclear tests in 1998, effectively securing the status of a nuclear-armed state, and Pakistan also joined the ranks of possessors through reciprocal nuclear tests in 1998. Neither country joined the NPT, and India was partially allowed civilian nuclear cooperation through the 2008 International Atomic Energy Agency (IAEA) Additional Protocol and Nuclear Suppliers Group exception measures. Israel has never officially confirmed possession of nuclear weapons, but many international research institutions assess it as a possessor state. North Korea withdrew from the NPT in 2003 and conducted six nuclear tests from its first in 2006 through 2017, establishing itself as a de facto nuclear-armed state.

History of nuclear weapons development

Nuclear weapons were first completed in 1945 through the United States' Manhattan Project and were used on Hiroshima and Nagasaki in Japan. Subsequently, the Soviet Union (1949), the United Kingdom (1952), France (1960), and China (1964) succeeded in nuclear tests one after another, and during the Cold War concerns spread that the number of nuclear-armed states would increase rapidly. To prevent such proliferation, the NPT emerged, and in 1996 the Comprehensive Nuclear-Test-Ban Treaty (CTBT) was adopted, but it has not yet entered into force due to refusal to ratify by the United States, China, Iran, Israel, and others. South Africa, Kazakhstan, Ukraine, and Belarus are representative cases of giving up or transferring nuclear weapons, and Ukraine's case is frequently cited in later debates over security assurances.

Deterrence theory and extended deterrence

The core logic of nuclear possession is deterrence. According to the concept of mutual assured destruction (MAD), if both sides possess second-strike capabilities, the costs of nuclear war outweigh the benefits and actual use is deterred. In addition, the United States provides extended deterrence (nuclear umbrella) to its allies, and under NATO's nuclear sharing arrangement, Germany, Italy, Belgium, the Netherlands, Turkey, and others participate in the operation of tactical nuclear weapons. South Korea and Japan are also representative cases relying on U.S. extended deterrence, and recently institutional reinforcement such as the Nuclear Consultative Group (NCG) has been discussed.

International norms and sanctions regime

Centered on the NPT, IAEA safeguards, the Nuclear Suppliers Group, and UN Security Council resolutions form the three main pillars of nuclear non-proliferation. Sanctions on economy, finance, and arms trade are imposed on violating states, with Iran and North Korea as representative targets. Meanwhile, the Treaty on the Prohibition of Nuclear Weapons (TPNW), adopted in 2017 and entered into force in 2021, is an attempt to outlaw nuclear weapons themselves, and nuclear-armed states and most NATO member states did not participate.

Latest trends

The nuclear order in 2024–2025 is assessed as having entered its most unstable phase since the end of the Cold War. The Stockholm International Peace Research Institute (SIPRI) pointed out in its 2024 and 2025 reports that global nuclear warhead inventories have turned to increase again and that the proportion of operationally deployed warheads is rising. Russia revised its nuclear doctrine in 2024 to state that nuclear response is possible even when a non-nuclear state conducts a conventional attack with the support of a nuclear-armed state, and it raised the level of pressure by deploying tactical nuclear weapons on Belarusian territory. New START, the only nuclear disarmament treaty between the United States and Russia, faces expiration in February 2026 and follow-up negotiations are virtually deadlocked.

North Korea signed a comprehensive strategic partnership treaty with Russia in 2024, suggesting the possibility of nuclear and missile cooperation, and is pushing to make its nuclear-armed state status a fait accompli, including specifying the strengthening of nuclear forces in its constitution. As the U.S. Department of Defense assesses that China will increase its operationally deployed nuclear warheads to more than 1,000 by 2030, a three-way nuclear competition structure appears to be forming. Iran has raised its uranium enrichment level to 60%, approaching weapons-grade material, and discussions on nuclear armament or expanding nuclear sharing are being publicly raised in Saudi Arabia, South Korea, Japan, Poland, and elsewhere. In 2025, the possibility of resuming nuclear tests was mentioned in the United States, and controversy over the effectiveness of the CTBT regime grew again.