Nuclear Forces

The Manhattan Project, a wartime collaboration led by the United States with British and Canadian participation, produced the first fission weapons. It established that a nuclear arsenal requires a large scientific-industrial complex for fissile material, either reactors and reprocessing for plutonium or uranium enrichment facilities.

The audit found the United States spent $11.9 trillion in present-day terms on nuclear weapons programmes between 1940 and 1996, of which 57 per cent went on delivery systems. Only about 7 per cent, $820 billion, was spent on the warheads themselves, showing that delivery dominates the cost of nuclear force.

On 6 August 1945 a uranium gun-type fission bomb, Little Boy, was dropped on Hiroshima, and on 9 August a plutonium implosion bomb, Fat Man, on Nagasaki, killing an estimated 100,000 to 246,000 people, mostly civilians, and prompting Japan's surrender days later. These remain the only combat uses of nuclear weapons and demonstrated both weapon designs in operational form, delivered by the simplest method, a gravity bomb from aircraft.

Since the atomic bombings of 1945, nuclear weapons have been detonated over 2,000 times for testing and demonstration purposes. Testing was the principal means by which states validated warhead designs and signalled capability.

More than 500 atmospheric weapons tests were conducted at sites around the world between 1945 and 1980. The resulting fallout became a major driver of public opposition and of the treaty regime that pushed testing underground.

In the early 1950s the US Livermore Laboratory drew up plans to test two massive devices, Gnomon at one gigaton and Sundial at ten gigatons of TNT equivalent. Neither was built, but they mark the upper conceptual limit of warhead yield explored during the arms race.

External boosting allowed the Soviet Union to deploy the first partially thermonuclear weapons. The technique is now obsolete because it demands a spherical bomb geometry, adequate only in the 1950s when bomber aircraft were the sole delivery vehicles.

The Ivy Mike test in the Marshall Islands used fusion to reach a yield far beyond any fission weapon, opening a race to build deliverable hydrogen bombs that the Soviet Union matched within a few years.

The 1954 Castle Bravo hydrogen bomb test at the Pacific Proving Grounds contaminated the crew and catch of a Japanese fishing boat. It first drew broad public attention to radioactive fallout and catalysed anti-nuclear movements, including Japan's unified council against atomic and hydrogen bombs formed the same year.

Issued on 9 July 1955, the manifesto was signed by eleven preeminent intellectuals including Albert Einstein days before his death. It launched the movement that led to the first Pugwash Conference on Science and World Affairs in July 1957.

The R-7 Semyorka, best known for launching Sputnik months later, gave the Soviet Union a missile able to strike the continental United States directly, ending the geographic protection distance had previously provided.

The IAEA was created in 1957 under UN mandate to encourage peaceful nuclear technology, provide international safeguards against misuse and facilitate safety measures. It became the principal institution monitoring the boundary between civil and weapons-related nuclear activity.

At Easter 1958 several thousand people marched four days from Trafalgar Square to the Atomic Weapons Research Establishment at Aldermaston. The marches continued into the late 1960s, drawing tens of thousands and becoming the emblem of British anti-nuclear protest.

Gerboise Bleue, detonated in French Algeria, made France the fourth nuclear-armed state and the basis for an independent deterrent that later underpinned its withdrawal from NATO's integrated military command.

USS George Washington carried out the first Polaris patrol, adding a concealed, mobile sea-based leg to nuclear forces that was far harder for an adversary to locate and destroy than land-based missiles or bombers.

Both superpowers carried out a number of peaceful nuclear explosions during the 1960s and 1970s for civil engineering and resource purposes. Their definitions and limits were codified in the Peaceful Nuclear Explosions Treaty of 1976.

The 1962 Starfish Prime high-altitude test produced an unexpected effect subsequently named the nuclear electromagnetic pulse. The discovery added a new category of weapon effect relevant to targeting and to hardening of military systems.

Pauling received the 1962 Nobel Peace Prize for his campaign against atmospheric nuclear testing, and the Ban the Bomb movement spread. Popular pressure contributed to the ratification of the Partial Test Ban Treaty the following year.

The 1963 treaty restricted all nuclear testing to underground detonations in order to prevent contamination from fallout. It was the first major constraint on how nuclear forces could be developed and validated.

The test made China the fifth state to demonstrate a nuclear weapon, following a programme pursued despite the Sino-Soviet split, and laid the foundation for its long-standing declaratory policy of no first use.

The Treaty of Pelindaba prohibits nuclear weapons in many African countries. It is one of the regional nuclear-weapon-free zones that constrain where warheads may be produced or deployed.

A Skyhawk attack aircraft carrying a nuclear weapon fell into the sea in 1965. The Pentagon did not reveal the loss of the one-megaton bomb until 1989.

In January 1966 a B-52G carrying nuclear weapons collided with a KC-135 tanker during mid-air refuelling off Spain, killing the tanker crew. Non-nuclear explosives in two weapons detonated on impact, contaminating a two-square-kilometre area with radioactive plutonium.

The 1967 treaty prohibited any production or deployment of nuclear weapons in Latin America and the Caribbean. It was the first regional nuclear-weapon-free zone covering a populated region.

The NPT restricted the activities signatories could undertake, allowing transfer of non-military nuclear technology without fear of proliferation. One explicit condition requires all signatories to pursue negotiations in good faith towards complete disarmament.

The Minuteman III intercontinental ballistic missile entered service able to strike several targets from a single launch, multiplying the number of warheads a given missile force represented without adding new missiles.

The test at Pokhran, described by New Delhi as a peaceful nuclear explosion, was the first by any country outside the group defined by the Non-Proliferation Treaty, and shaped decades of subsequent non-proliferation policy.

Because high-energy neutrons penetrate dense matter such as tank armour, neutron warheads were procured in the 1980s as tactical payloads for 200 mm W79 and 155 mm W82 artillery shells and short-range missile forces. They were never deployed in Europe.

In September 1980 a Titan missile equipped with a nuclear warhead exploded in its silo at Damascus, Arkansas. It is among the best-known accidents illustrating the safety risks of maintaining deployed strategic forces.

Israel struck a nuclear reactor under construction at Osirak in 1981, describing it as an attempt to halt Iraqi nuclear arms ambitions. A comparable strike was carried out against a reactor under construction in Syria in 2007.

The total worldwide stockpile reached its maximum of over 64,000 warheads in 1986 before declining to roughly 9,600 by 2025. The peak marks the high point of Cold War force accumulation, after which arms control and unilateral reductions took effect.

The last treaty capping deployed US and Russian strategic warheads and launchers was due to lapse, with no negotiations underway on a replacement. Both sides signalled intent to observe its central numerical limits informally rather than extend a binding framework.

US defence assessments described ongoing fielding of intercontinental ballistic missiles across silo complexes built earlier in the decade in Gansu and Inner Mongolia, part of an expansion projected to bring China's warhead stockpile towards roughly 1,000 by 2030.

On 30 October 2025 the US President called for renewed nuclear testing to keep pace with Russia and China. It was not made clear whether he meant nuclear explosive testing or testing of delivery systems for warheads.

Kim Jong Un was shown at a shipyard beside a large submarine hull that state media said would be nuclear-powered, a step beyond the diesel-electric boats North Korea has used to trial submarine-launched ballistic missiles.

Following a cost overrun that breached statutory limits the previous year, the Air Force revised the programme intended to replace the ageing Minuteman III fleet, concentrating changes on launch-control and silo infrastructure rather than the missile itself.

Commercial satellite imagery of the Huludao shipyard showed continued work consistent with the Type 096 programme, expected to succeed the current Type 094 fleet and carry a longer-range submarine-launched missile once it enters service.

Washington sanctioned the National Development Complex and associated suppliers, citing concern over long-range ballistic missile work. US officials said the programme's trajectory could eventually extend beyond the India-focused deterrent Pakistan has traditionally maintained.

The intermediate-range ballistic missile struck a defence facility at Dnipro in Ukraine. President Putin said the weapon, capable of carrying nuclear or conventional warheads, was fielded outside the limits of the lapsed Intermediate-Range Nuclear Forces Treaty.

State media described the missile as the country's most powerful long-range system yet. Its solid-fuel design shortens launch preparation time compared with North Korea's older liquid-fuel missiles, improving survivability against pre-emptive strikes.

Open-source analysts identified a large crater at the Sarmat heavy intercontinental ballistic missile's silo complex, consistent with an explosion during launch preparations. The missile, intended to replace the Soviet-era Voevoda, has had a troubled test record.

The Arihant-class boat joined the fleet alongside its sister vessel, strengthening the sea-based leg of India's nuclear triad. Analysts noted that patrols remain far less frequent than those of the established nuclear-armed navies.

As of 2024 Russia escalated nuclear threats over Ukraine and was reported to be planning to place nuclear weapons in orbit, which would breach the 1967 Outer Space Treaty. This would represent a new class of delivery basing beyond the established triad.

China is significantly enlarging its nuclear forces, with projections of more than 1,000 warheads by 2030 and up to 1,500 by 2035. The build-up alters the long-standing bipolar structure of global nuclear force.

The June 2019 Pentagon publication stated that integration of nuclear weapons employment with conventional and special operations forces is essential to mission success. It formalised the blending of nuclear and conventional force planning.

As of early 2019, more than 90 per cent of the world's 13,865 nuclear weapons were owned by Russia and the United States. The concentration reflects the enduring Cold War legacy of the two largest arsenals.

In 2017, 122 states, mainly in the Global South, voted to adopt the TPNW, which entered into force in 2021. No nuclear-armed state joined, but the treaty created a formal legal norm against possession.

North Korea announced in January 2016 that it had tested a fusion weapon, though the claim is disputed. It marked the regime's assertion of thermonuclear rather than merely fission capability.

In an April 2009 speech in Prague the US President endorsed the goal of a world without nuclear weapons. It gave political weight to post-Cold War abolition campaigns such as Global Zero.

In 2006 the Central Asian states created a nuclear-weapon-free zone prohibiting nuclear weapons on their territory. It extended the zone framework into the post-Soviet space.

The underground test at Punggye-ri followed North Korea's withdrawal from the Non-Proliferation Treaty three years earlier. The declared yield was small and disputed, but the test confirmed a warhead programme built largely outside independent verification.

One stated casus belli for the 2003 Iraq War was a US accusation that Iraq was actively pursuing nuclear weapons. The programme was soon discovered to have been discontinued.

UNODA was created in January 1998 under Secretary-General Kofi Annan's UN reform plan, presented to the General Assembly in July 1997. It became the UN's institutional focus for disarmament, including nuclear weapons.

In 1998 the Department of Energy revealed that the United States had made a substantial past investment in developing a pure fusion weapon. It stated that no credible design had resulted and that the US neither possesses nor is developing such a weapon.

India's Pokhran-II series and Pakistan's Chagai-I tests turned two long-suspected weapons programmes into declared nuclear arsenals, prompting Western sanctions and cementing an overt nuclear rivalry in South Asia that persists today.

Since 1996 the United States has permitted the targeting of its nuclear weapons at terrorists armed with weapons of mass destruction. The shift responded to arguments that post-Cold War threats required a strategy distinct from classical deterrence.

The ICJ found that use or threat of use of nuclear weapons would generally be contrary to the rules of international law applicable in armed conflict. It declined to rule on extreme circumstances where the survival of a state was at stake.

The CTBT prohibits all testing of nuclear weapons, including explosions for peaceful purposes. It requires ratification by 44 specified states to enter into force; as of 2012 eight of these had still not ratified, leaving the treaty stalled.

The 1991 Presidential Nuclear Initiatives were non-binding reciprocal announcements that reduced deployed forces, especially tactical weapons. They sit alongside binding treaties such as INF, START I, SORT and New START in the arms control architecture.

The 1990 Act made the United States the only nation compensating nuclear test victims. More than $1.38 billion in compensation had been approved as of March 2009.

In January 1986 the Soviet leader publicly proposed abolishing the world's nuclear weapons by the end of the twentieth century in three stages. The proposal framed superpower disarmament diplomacy in the final Cold War years.