Nuclear weapons of the United States
Under the Manhattan Project, the United States was the first country to manufacture nuclear weapons and is the only country to have used them in combat, with the bombings of Hiroshima and Nagasaki in World War II against Japan. In total it conducted 1,054 nuclear tests, and tested many long-range nuclear weapons delivery systems.
The United States currently deploys 1,770 warheads, mostly under Strategic Command, to its nuclear triad: Ohio-class submarines with Trident II submarine-launched ballistic missiles, silo-based Minuteman III intercontinental ballistic missiles, and B-2 Spirit and B-52 Stratofortress bombers armed with B61 and B83 bombs and AGM-86B cruise missiles. The US maintains a limited anti-ballistic missile capability via the Ground-Based Interceptor and Aegis systems. The US plans to modernize its triad with the Columbia-class submarine, Sentinel ICBM, and B-21 Raider, from 2029.
The US currently stations nuclear weapons in the form of B61 bombs in six European NATO countries: Belgium, Germany, Italy, the Netherlands, Turkey, and United Kingdom; it extends a nuclear umbrella to South Korea, Japan, and Australia.
Throughout the Cold War, the US and USSR competed in the nuclear arms race. From 1951, the US became the first country to develop thermonuclear weapons. From 1954, the US stationed nuclear weapons in at least 17 other countries, in NATO against the Warsaw Pact, and South Korea, Japan, Taiwan, and the Philippines against China. During the 1950s, Strategic Air Command operated hundreds of strategic bombers. By the 1960s, ICBMs were deployed in silos, such as the Atlas and Titan, and aboard submarines as Polaris. The 1962 Cuban Missile Crisis was regarded as an exceptionally close call that could have resulted in a nuclear exchange and World War III. The nuclear arsenal continued to grow, including to potential space-based systems with the 1980s Strategic Defense Initiative, but was curtailed as the Cold War ended, partly by treaties including as START I. Its successor, New START, will expire in 2026.
Between 1940 and 1996, the federal government spent at least US$ in present-day terms on nuclear weapons, delivery systems, command and control, maintenance, waste management and administration. The US has produced more than 70,000 nuclear warheads, more than all other nuclear weapon states combined. Design takes place at Los Alamos, Livermore, and Sandia laboratories, while tests were conducted at Nevada Test Site and Pacific Proving Grounds. Until the 1963 Partial Nuclear Test Ban Treaty, the vast majority of tests were atmospheric. Subsequent underground testing limited nuclear fallout. The United States declared a unilateral testing moratorium in 1992 and signed the Comprehensive Nuclear-Test-Ban Treaty in 1996, but has not ratified it. Science-Based Stockpile Stewardship shifted focus from continual weapon redesigns to limiting aging, via supercomputer simulation and physics experiments such as inertial confinement fusion.
Production and testing sites radioactively contaminated civilian communities: Marshall Islanders were compensated at least US$759 million for testing exposure, and US citizens have been compensated over US$2.5 billion.
, the US and Russia possess a comparable number of warheads; together more than 90% of the world's stockpile. The United States holds 1,770 deployed, 1,930 in reserve, and 1,477 retired and awaiting dismantlement, in total 5,177. The projected costs for maintaining US nuclear forces are $60 billion per year during the 2021–2030 period.
On October 30, 2025, President Trump called on the Pentagon to resume testing nuclear weapons immediately, though it was unclear whether this referred to nuclear explosive testing or testing of nuclear delivery systems.
Development history
Manhattan Project
The United States first began developing nuclear weapons during World War II under the order of President Franklin Roosevelt in 1939, motivated by the fear that they were engaged in a race with Nazi Germany to develop such a weapon. After a slow start under the direction of the National Bureau of Standards, at the urging of British scientists and American administrators, the program was put under the Office of Scientific Research and Development, and in 1942 it was officially transferred under the auspices of the United States Army and became known as the Manhattan Project, an American, British and Canadian joint venture. Under the direction of General Leslie Groves, over thirty different sites were constructed for the research, production, and testing of components related to bomb-making. These included the Los Alamos National Laboratory at Los Alamos, New Mexico, under the direction of physicist Robert Oppenheimer, the Hanford plutonium production facility in Washington, and the Y-12 National Security Complex in Tennessee.By investing heavily in breeding plutonium in early nuclear reactors and in the electromagnetic and gaseous diffusion enrichment processes for the production of uranium-235, the United States was able to develop three usable weapons by mid-1945. The Trinity test was a plutonium implosion-design weapon tested on 16 July 1945, with around a 20 kiloton yield.
Faced with a planned invasion of the Japanese home islands scheduled to begin on 1 November 1945 and with Japan not surrendering, President Harry S. Truman ordered the atomic raids on Japan. On 6 August 1945, the US detonated a uranium-gun design bomb, Little Boy, over the Japanese city of Hiroshima with an energy of about 15 kilotons of TNT, killing approximately 70,000 people, among them 20,000 Japanese combatants and 20,000 Korean forced laborers, and destroying nearly 50,000 buildings. Three days later, on 9 August, the US attacked Nagasaki using a plutonium implosion-design bomb, Fat Man, with the explosion equivalent to about 20 kilotons of TNT, destroying 60% of the city and killing approximately 35,000 people, among them 23,200–28,200 Japanese munitions workers, 2,000 Korean forced laborers, and 150 Japanese combatants.
On 1 January 1947, the Atomic Energy Act of 1946 took effect, and the Manhattan Project was officially turned over to the United States Atomic Energy Commission.
On 15 August 1947, the Manhattan Project was abolished.
During the Cold War
The American atomic stockpile was small and grew slowly in the immediate aftermath of World War II, and the size of that stockpile was a closely guarded secret. However, there were forces that pushed the United States towards greatly increasing the size of the stockpile. Some of these were international in origin and focused on the increasing tensions of the Cold War, including the loss of China, the Soviet Union becoming an atomic power, and the onset of the Korean War. And some of the forces were domestic – both the Truman administration and the Eisenhower administration wanted to rein in military spending and avoid budget deficits and inflation. It was the perception that nuclear weapons gave more "bang for the buck" and thus were the most cost-efficient way to respond to the security threat the Soviet Union represented.As a result, beginning in 1950 the AEC embarked on a massive expansion of its production facilities, an effort that would eventually be one of the largest US government construction projects ever to take place outside of wartime. And this production would soon include the far more powerful hydrogen bomb, which the United States had decided to move forward with after an intense debate during 1949–50. as well as much smaller tactical atomic weapons for battlefield use.
By 1990, the United States had produced more than 70,000 nuclear warheads, in over 65 different varieties, ranging in yield from around.01 kilotons to the 25 megaton B41 bomb. Between 1940 and 1996, the US spent at least $ in present-day terms on nuclear weapons development. Over half was spent on building delivery mechanisms for the weapon. $ in present-day terms was spent on nuclear waste management and environmental remediation.
Richland, Washington was the first city established to support plutonium production at the nearby Hanford nuclear site, to power the American nuclear weapons arsenals. It produced plutonium for use in cold war atomic bombs.
Throughout the Cold War, the US and USSR threatened with all-out nuclear attack in case of war, regardless of whether it was a conventional or a nuclear clash. US nuclear doctrine called for mutually assured destruction, which entailed a massive nuclear attack against strategic targets and major populations centers of the Soviet Union and its allies. The term "mutual assured destruction" was coined in 1962 by American strategist Donald Brennan. MAD was implemented by deploying nuclear weapons simultaneously on three different types of weapons platforms.
Post–Cold War
After the 1989 end of the Cold War and the 1991 dissolution of the Soviet Union, the US nuclear program was heavily curtailed; halting its program of nuclear testing, ceasing its production of new nuclear weapons, and reducing its stockpile by half by the mid-1990s under President Bill Clinton. Many former nuclear facilities were closed, and their sites became targets of extensive environmental remediation. Efforts were redirected from weapons production to stockpile stewardship; attempting to predict the behavior of aging weapons without using full-scale nuclear testing. Increased funding was directed to anti-nuclear proliferation programs, such as helping the states of the former Soviet Union to eliminate their former nuclear sites and to assist Russia in their efforts to inventory and secure their inherited nuclear stockpile. By February 2006, over $1.2 billion had been paid under the Radiation Exposure Compensation Act of 1990 to US citizens exposed to nuclear hazards as a result of the US nuclear weapons program, and by 1998 at least $759 million had been paid to the Marshall Islanders in compensation for their exposure to US nuclear testing. Over $15 million was paid to the Japanese government following the exposure of its citizens and food supply to nuclear fallout from the 1954 "Bravo" test. In 1998, the country spent an estimated $35.1 billion on its nuclear weapons and weapons-related programs.In the 2013 book Plutopia: Nuclear Families, Atomic Cities, and the Great Soviet and American Plutonium Disasters, Kate Brown explores the health of affected citizens in the United States, and the "slow-motion disasters" that still threaten the environments where the plants are located. According to Brown, the plants at Hanford, over a period of four decades, released millions of curies of radioactive isotopes into the surrounding environment. Brown says that most of this radioactive contamination over the years at Hanford were part of normal operations, but unforeseen accidents did occur and plant management kept this secret, as the pollution continued unabated. Even today, as pollution threats to health and the environment persist, the government keeps knowledge about the associated risks from the public.
During the presidency of George W. Bush, and especially after the 11 September terrorist attacks of 2001, rumors circulated in major news sources that the US was considering designing new nuclear weapons and resuming nuclear testing for reasons of stockpile stewardship. Republicans argued that small nuclear weapons appear more likely to be used than large nuclear weapons, and thus small nuclear weapons pose a more credible threat that has more of a deterrent effect against hostile behavior. Democrats counterargued that allowing the weapons could trigger an arms race. In 2003, the Senate Armed Services Committee voted to repeal the 1993 Spratt-Furse ban on the development of small nuclear weapons. This change was part of the 2004 fiscal year defense authorization. The Bush administration wanted the repeal so that they could develop weapons to address the threat from North Korea. "Low-yield weapons" were permitted to be developed. The Bush administration was unsuccessful in its goal to develop a guided low-yield nuclear weapon, however, in 2010 President Barack Obama began funding and development for what would become the B61-12, a smart guided low-yield nuclear bomb developed off of the B61 “dumb bomb”.
Statements by the US government in 2004 indicated that they planned to decrease the arsenal to around 5,500 total warheads by 2012. Much of that reduction was already accomplished by January 2008.
According to the Pentagon's June 2019 Doctrine for Joint Nuclear Operations, "Integration of nuclear weapons employment with conventional and special operations forces is essential to the success of any mission or operation."
In 2024 it was estimated that the United States possessed 1,770 deployed nuclear warheads, 1,938 in reserve, and 1,336 retired and awaiting dismantlement. 1,370 strategic warheads were deployed on ballistic missiles, 300 at strategic bomber bases in the United States, and 100 tactical bombs at air bases in Europe.