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There are nine countries in the world that have nuclear weapons. Between them they possess an estimated 15,000 nuclear warheads. Of those, four countries: China, India, Pakistan and North Korea are actively expanding their nuclear capabilities.

Their nuclear status within the international community differs significantly however. Under the Nuclear Non-Proliferation Treaty (NPT) a nuclear weapon state is defined as one that manufactured and exploded a nuclear weapon, or other nuclear explosive device, prior to 1 January 1967. As such there are five acknowledged nuclear weapon states under the treaty: the United States, Russia, China, France and the UK. Those countries which have developed a nuclear capability outside of the NPT framework are considered de facto nuclear weapon states. At present there are three states that have pursued this path: India, Pakistan and Israel. Despite having conducted a series of nuclear tests and demonstrated its missile capabilities, North Korea is not recognised by the international community as a nuclear weapons state. It is considered nuclear capable, however. In addition there are a number of states that have, over the years, had nuclear aspirations, the most prominent being Iran.

This paper is intended as a brief guide to which countries possess nuclear weapons and how they are seeking to either modernise or expand those capabilities.

United States

The United States conducted its first nuclear test in July 1945 and is the only country to have used nuclear weapons in conflict when it dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki in August 1945.

By the time the NPT was concluded in 1968 the United States had a nuclear stockpile of tens of thousands. Since the 1970s the US and Soviet Union/Russia have concluded a number of bilateral arms control agreements which have reduced the size of their respective nuclear arsenals.

Despite this progress the United States still retains an extensive nuclear force (6,800 nuclear warheads in total) and is in the process of replacing or modernising its nuclear capabilities through an extensive programme that is estimated to cost $400 billion over the next decade and $1 trillion in total over the next 30 years.


The Soviet Union tested its first atomic weapon in 1949. By the time the NPT was concluded in 1968, the Soviet Union, like the US, had accumulated a nuclear stockpile of tens of thousands of warheads.

During the last two decades of the Cold War the US and the Soviet Union concluded a number of bilateral arms control agreements which reduced the size of their respective nuclear arsenals.

Following the dissolution of the Soviet Union in late 1991, Russia was formally recognised as the sole remaining nuclear weapon state under a Protocol to the US-Soviet Strategic Arms Reduction Treaty, which was signed in May 1992.

Russia has the largest nuclear arsenal in the world (approximately 7,000 warheads) and since 2008 has been undertaking an extensive programme of nuclear capabilities modernisation.


In 1955 the Chinese leadership initiated a nuclear weapons programme, partly in response to concerns about US nuclear threats during the Korean War. Nine years later, China became the last of the five NPT recognised states to successfully test an atomic device. China then tested its first thermonuclear device in June 1967. Observers commented on the short time-span (32 months) between the two tests, which was substantially less than the other nuclear powers. 

Precise information on the extent of China’s nuclear arsenal is difficult to obtain, due to a lack of open source information and often contradictory or exaggerated claims.

China’s nuclear stockpile is estimated at 270 warheads. Over the last two decades China has, however, been actively seeking to expand its nuclear capabilities in order to achieve a more robust and survivable nuclear force; while at the same time developing a credible second-strike capability. It is the only acknowledged nuclear weapon state under the NPT that is expanding its nuclear inventory.


France first tested a nuclear weapon in 1960, eight years after the UK and four years before China. The last French tests took place in 1996, just prior to the conclusion of the Comprehensive Nuclear Test Ban Treaty (CTBT).

Since the end of the Cold War France has scaled back its nuclear arsenal by 50%, with a reduction in both its overall holdings but also the withdrawal of several weapons systems, including its land-based ballistic missile capability. It now has a nuclear stockpile of less than 300 warheads. It has also reduced its alert levels (in 1992 and 1996) in terms of both response times and the number of weapons systems on alert. All of France’s nuclear forces have been de-targeted.

France does not participate in NATO’s nuclear planning mechanisms and its forces are not formally assigned to NATO.


The UK first tested a nuclear explosive device in October 1952, becoming the third state to develop nuclear weapons after the United States and the Soviet Union.

Initial capability centred upon the RAF’s strategic bomber force. A submarine-launched capability, based upon the Polaris submarine-launched ballistic missile (SLBM), entered service in 1968. The current Trident-based system entered service in the mid-1990s.

Since the end of the Cold War, the UK has taken a number of steps towards nuclear disarmament. It has withdrawn all nuclear weapons systems except for Trident; made changes to the operational status of the deterrent and been increasingly transparent about its nuclear inventory. At present the UK’s nuclear stockpile is 225 warheads, although that will reduce to no more than 180 warheads by the mid-2020s. At this point the UK will have achieved a 65% reduction in the size of its overall nuclear stockpile since the height of the Cold War.

The UK is currently in the process of replacing its SSBN fleet, with a new class of submarine: the Dreadnought. The first submarine is due to enter service in the early 2030s.


Successive Indian governments had maintained a policy of ambiguity on the country’s nuclear status after what appeared to be a partially successful nuclear test in 1974. In May 1998, however, India conducted a series of publicised nuclear tests which established its status as a self-declared nuclear weapon state, outside of the framework of the NPT.

Public information on India’s nuclear weapons programme is, however, scarce. It is estimated to have an arsenal of between 120 and 130 nuclear warheads, although there is some doubt as to how many are operational. India continues to produce fissile material for weapons purposes and is actively working to expand both its nuclear arsenal and its delivery capabilities. In August 2016 it completed the ‘nuclear triad’, enabling delivery of a nuclear warhead by land, sea or air.


Pakistan’s nuclear programme began in the early 1970s, following the 1971 war with India that led to East Pakistan becoming Bangladesh. It was spurred on by India’s first nuclear test in 1974, although it was not until the late 1980s that the US concluded that Pakistan had acquired the capability to build a primitive nuclear device.

In line with India, Pakistan conducted a series of publicised nuclear tests in May 1998 which established its status as self-declared nuclear weapon state, outside of the NPT framework.

Pakistan is estimated to have a stockpile of 130-140 warheads. Like India, it continues to produce fissile material for weapons production and it is thought to be expanding its nuclear arsenal faster than any other country.


Successive Israeli governments have maintained a policy of official ambiguity on the issue of nuclear weapons. Israel has never demonstrated its capability through a nuclear test, nor has the country ever confirmed or denied having nuclear weapons.

Despite this, it is universally acknowledged that Israel possesses a nuclear weapons capability (approximately 80-100 warheads), outside of the framework of the NPT.

North Korea

Despite having conducted a number of nuclear tests North Korea is not recognised by the international community as a nuclear weapons state. It is, however, considered nuclear capable.

Opinions are divided on the size of its stockpile. A longstanding common estimate has been 8-10 warheads although US Defence Intelligence was reported in July 2017 to have revised that estimate significantly upwards to 60. Those recent figures have, however, been disputed by a number of independent experts.

North Korea possesses a short-to-medium range delivery capability capable of targeting locations in its immediate sphere of influence, including US forces in the Pacific. Achieving a viable long-range nuclear capability is currently its objective and in July 2017 North Korea successfully tested, for the first time, an ICBM technically capable of striking the United States. Further development to ensure reliability and accuracy is required, but experts have concluded that achieving a viable long-range capability is likely within the next 2 years, and much sooner than initial estimates had suggested. However, while North Korea is thought to have achieved miniaturisation of a nuclear warhead capable of being mounted on an ICBM, opinions still remain divided.

It continues to test both its nuclear warheads and its ballistic missile capabilities, in defiance of UN Security Council resolutions.

Other suspected aspirant nations


An extensive uranium enrichment programme was revealed in the early 00s, which many countries and other observers alleged was part of a nuclear weapons programme and not just intended for civilian energy purposes.

The International Atomic Energy Agency (IAEA) found Iran to be non-compliant with its NPT safeguards agreement in 2005 and referred the matter to the UN Security Council which passed several resolutions calling on Iran to halt its enrichment activities. However, in a report in 2011 the IAEA concluded that it was still unable to offer assurances about the purpose of Iran’s nuclear programme.

Concern over Iran’s potential threshold status has led to intense diplomatic efforts over the last few years to reach agreement on Iran’s nuclear programme, in exchange for the lifting of international sanctions which have been imposed against the regime since 2002.

A deal on Iran’s nuclear programme was eventually reached in 2015. In exchange for limitations on Iran’s enrichment activities, and access to all Iranian nuclear facilities by the IAEA, the UN, US and EU agreed to suspend all nuclear related sanctions against Iran.

The future of the Iran nuclear deal is currently uncertain after US President Donald Trump threatened to withdraw from the agreement. However, top officials in the Trump administration, including the US Defense Secretary, James Mattis, have expressed the view that Iran continues to abide by the nuclear agreement and that upholding it is in the US’ national security interests. Were the agreement to fall apart Iran’s President has stated that the country could restart its nuclear programme.   


Syria, which is also a party to the NPT, has been under investigation by the IAEA in response to concerns within the international community that it had been developing a secret nuclear weapons programme. However, verification and monitoring of suspected nuclear sites by IAEA inspectors has been complicated by the ongoing civil war. Nevertheless, in a statement to the 2015 NPT review conference the IAEA Director General renewed his call on Syria to cooperate fully with the IAEA in connection with unresolved nuclear issues.

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