Nuclear weapons are extremely powerful explosive devices that generate enormous amounts of energy by splitting or merging subatomic particles. They are many times more powerful than conventional bombs and are classified alongside certain types of chemical and biological armaments as weapons of mass destruction (WMDs). Nuclear weapons were first developed during the 1940s, and since that time, widespread speculation has posited that their extensive use in war could have devastating or even apocalyptic effects on human civilization and life on Earth. Thus, the international community has long sought ways to limit the continued development of nuclear weapons and reduce the chances of their detonation.
Types of Nuclear Weapons
Nuclear weapons use two different processes to generate their destructive force: fission and fusion. Fission weapons, also called atomic weapons or atomic bombs, create energy by using subatomic particles called neutrons to split the nuclei of uranium or plutonium isotopes. When a neutron strikes the nucleus, the atom breaks apart, releasing a large amount of energy as well as additional neutrons. These neutrons then split adjacent atoms contained within the weapon casing, triggering a self-sustaining, explosive chain reaction.
Fusion weapons, also known as thermonuclear bombs, hydrogen bombs, or H-bombs, generate energy by joining hydrogen atoms together in a process similar to the atomic fusion that powers the sun. Hydrogen bombs use nuclear fission as an initial trigger to create the scorching temperatures needed to achieve atomic fusion. Hydrogen bombs are much more destructive than atomic bombs and can create explosions that are hundreds of times more powerful.
Some weapons experts also distinguish between strategic and tactical nuclear weapons. Strategic nuclear weapons are designed to attack and destroy dense population centers and nuclear weapons stockpiles. They are designed to be delivered via long-range aircraft or guided missile systems. Tactical nuclear weapons are smaller weapons designed for use on a military battlefield and may include short-range missiles, artillery shells, or torpedoes. This distinction is controversial within the military community, with some authorities contending that nuclear weapons cannot be tactical in nature due to their immense destructive force.
The Origins of Disarmament Efforts
Nuclear weapons are powerful enough to level entire cities, and a single munition is capable of killing millions of people. Given nuclear weapons' dangerous profile, the United Nations (UN) has officially supported nuclear disarmament since its 1945 founding, which closely followed the only two occasions, as of 2020, in which nuclear weapons have been deployed in warfare. During World War II, the United States dropped atomic bombs on the Japanese cities of Hiroshima on August 6, 1945, and Nagasaki on August 9, 1945. Estimates suggest that more than three hundred thousand people, mostly civilians, died as a direct or indirect result of the nuclear bomb deployments. Japan surrendered unconditionally on August 15, 1945, ending the war, but President Harry S. Truman's decision to use atomic weapons was controversial.
In 1946 the UN General Assembly adopted the first resolution in its history, which created an internal commission to study and provide policy recommendations on the social and political problems arising from nuclear weapons. The resolution stated an objective of achieving "the elimination from national armaments of atomic weapons and of all other major weapons adaptable to mass destruction." The UN has described its position as "disarmament to save humanity," as the Hiroshima and Nagasaki bombings provided a grim demonstration of the immense destructive force of nuclear weapons and their ability to inflict mass casualties. In addition to killing people upon impact, nuclear weapons have indirect adverse health effects that can lead to death: victims can suffer fatal burns and radiation poisoning, and those exposed to the high levels of radiation these bombs release face an elevated risk of developing cancer for the rest of their lives.
The Cold War and Nuclear Deterrence
Despite the UN's position, the postwar era would be defined by the proliferation of nuclear weapons among the world's opposing superpowers, the United States and the Soviet Union. The competing nations' nuclear arms race was a central feature of the Cold War (1945–1989), in which the United States and the Soviet Union engaged in an ideological, economic, and technological rivalry. In 1949 the Soviet Union conducted its first nuclear weapons tests, bringing about an early escalation of Cold War tensions. The Cold War went on to dominate world politics over the next four decades, with the United States and the Soviet Union striving to outdo each other in developing larger and more sophisticated nuclear weapons stockpiles as well as advanced rocket missile technologies capable of delivering them across long distances.
As the Cold War progressed, the nuclear weapon arsenals of the United States and the Soviet Union grew large enough to destroy each other many times over. Analysts speculate that this may have prevented outright war between the two countries, as leaders of both nations were unwilling to risk a nuclear response to an attack. The concept of using the threat of nuclear weapons to deter others from using them became known as nuclear deterrence or the "mutual assured destruction" (MAD) theory of nuclear weapons. Though war may have been averted, a vocal minority in the United States continued to condemn nuclear weapons as fundamentally immoral and sought to limit or eliminate America's nuclear arsenal. These sentiments echoed the official UN position on nuclear weapons and helped instigate the negotiation and implementation of multiple nuclear arms control treaties. International control measures took on heightened urgency as the Cold War intensified during the 1950s and 1960s and three other countries—the United Kingdom (1952), France (1960), and China (1964)—officially became nuclear states.
Arms Control Treaties
International arms-control treaties have sought to stop nuclear weapons testing, avoid proliferation to nonnuclear nations, and limit or reduce the numbers of weapons in nuclear states. Many argue these treaties act as a deterrent, however critics argue such treaties do not provide sufficient protection, because some nations may not adhere to their treaty promises. Such treaties began with the Antarctic Treaty of 1959, which declared Antarctica a demilitarized international zone, precluding any possibility of its use as a nuclear weapons testing or storage site. Another important early agreement is the Limited Test Ban Treaty of 1963, signed by the United States, United Kingdom, and Soviet Union, which banned nuclear test explosions in the atmosphere, outer space, and underwater.
In 1968 the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) opened for ratification. The landmark treaty created strict limits on the spread of militarized nuclear technologies beyond the five established nuclear states. As of April 2020, all but four of the world's countries had ratified the NPT, which went into effect in 1970 and was indefinitely extended in 1995. The holdouts include Israel, India, and Pakistan, while North Korea withdrew from the agreement in 2003. All four countries are known or suspected of leveraging their outsider status to develop their own nuclear weapons stockpiles. South Sudan has not ratified the NPT but is not suspected of having nuclear weapons, however Iran, which did sign the treaty, is suspected of attempting to develop nuclear weapons. The NPT authorized the International Atomic Energy Agency (IAEA) to verify that countries do not use nuclear energy materials in nuclear weapons programs.
By the late 1980s, the Soviet Union was on the brink of dissolution, which formally occurred in 1991. This signaled the end of the Cold War, and significant progress was made to reduce testing and numbers of nuclear weapons in the 1990s. In 1996, the UN approved the Comprehensive Nuclear-Test-Ban Treaty (CTBT), which would ban all testing of nuclear weapons. A total of 168 out of 196 countries, including Russia in 2000, had ratified the CTBT by April 2020. The treaty will not take effect, however, until it is ratified by all 44 countries with nuclear reactors or power generators. As of 2020, three of these have yet to sign the CTBT. An additional five—including the United States—have signed but not ratified the treaty. However, many argue it has still served as a voluntary moratorium on nuclear weapons testing. In 1996 the former Soviet states of Ukraine, Belarus, and Kazakhstan transferred the nuclear weapons within their borders to Russia, and both Russia and the United States took steps to "stand down" the nuclear armaments they had amassed over the course of the Cold War. Relations between the United States and Russia continued to improve, leading to the Strategic Offensive Reductions Treaty (SORT) of 2003, also known as the "Moscow Treaty." This agreement called for both nations to reduce their nuclear arsenals to between 1,700 and 2,200 warheads by 2012.
In 2010 SORT was superseded by an agreement known as the New START (Strategic Arms Reduction Treaty). Signed by US president Barack Obama (1961–) and Russian leader Dmitry Medvedev (1965–), New START came into effect in 2011 and required both signatories to bring their nuclear weapons stockpiles and delivery systems to new lows by 2018. However, upon taking office in 2017, US president Donald Trump (1946–) expressed dissatisfaction with the treaty to his Russian counterpart, Vladimir Putin (1952–). New START is scheduled to expire in 2021.
The Rise of Rogue Nuclear States
The international community has expressed concern over the actions of so-called rogue nuclear states, which are known or thought to have developed nuclear weapons programs that contravene the terms of nuclear nonproliferation treaties. From the United States' perspective, two nations pose a particular threat: Iran and North Korea.
In 1957 Iran entered a civil nuclear cooperation agreement with the United States. Through this agreement, Iran was able to acquire its first kilograms of enriched uranium, a material required to create a nuclear weapon. During the 1960s and 1970s, Iran and the United States were strong allies, but Iran's 1979 Islamic Revolution began the breakdown of amicable relations between the two countries. Iran continued to expand its nuclear program following the Islamic Revolution, and by the 1990s, the United States expressed concern about the program.
Since 2003, the Iranian government has maintained that its nuclear program is strictly limited to civilian purposes including power generation and cancer research. However, the United States and several European powers remained skeptical. In 2006 the UN imposed sanctions on Iran for its repeated violations of the NPT, to which Iran is signatory. By 2009 experts believed the Iranian nuclear program had produced enough low-enriched uranium to build nuclear weapons.
In response to international pressure and stiff economic sanctions, Iran agreed to a Joint Comprehensive Plan of Action (JCPOA) in 2015 with China, France, Germany, the Russian Federation, the United Kingdom, and the United States to limit its uranium enrichment stockpiles in exchange for the removal of several crippling economic sanctions, including those imposed by the European Union. President Trump was heavily critical of the agreement, which was negotiated by President Obama. Trump pledged to "dismantle the disastrous deal," citing Iran's technical violations of several of its clauses. In 2018 the Trump administration again imposed nuclear-related economic sanctions on Iran, prompting Iran to threaten to cease to abide by the terms of the JCPOA in 2019. However, the IAEA reported that Iran was still cooperating with the terms of the JCPOA as of March 2020. The situation remains unresolved as of April 2020, and Iran has threatened to withdraw from the NPT if Western powers follow through on their threats to bring Iran's alleged violations before the UN Security Council.
Meanwhile, North Korea has maintained an active nuclear weapons program since its withdrawal from the NPT in 2003. Upon North Korea's withdrawal, five countries—the United States, China, Russia, Japan, and South Korea—initiated talks with North Korea with the goal of denuclearizing the entire Korean Peninsula. The Six-Party Talks were successful in persuading North Korea to close its main nuclear reactor in 2007, but negotiations were suspended in 2009 after North Korea reactivated its nuclear facilities. Tensions abated temporarily in 2012 when North Korea agreed to suspend several components of its nuclear program in exchange for food aid from the United States. However, the agreement was nullified two months later following a rocket launch dispute between the two countries.
North Korea has continued to expand its nuclear program, stoking international tensions. In 2015 North Korean officials stated they had the ability to strike the US mainland and would do so if necessary, and North Korean state media declared in December 2015 that it had hydrogen bombs in its weapons arsenal. Tensions intensified in 2017 during the early months of the Trump presidency, with North Korea threatening to strike the United States. While bilateral diplomacy succeeded in easing the tensions, North Korea continued to develop and test nuclear weapon systems in 2018 and 2019, with North Korean state military exercises in March 2020 appearing to include nuclear-enabled missile launchers.
Nuclear Armament Under President Trump
As Cold War tensions eased during the late 1980s and early 1990s, the United States and other members of the North Atlantic Treaty Organization (NATO) adopted military strategies that favored a "reduced reliance on nuclear weapons." The United States and NATO allies also committed to using nuclear weapons only as a "last resort." According to a 2019 worldwide assessment published by the Arms Control Association, the United States currently has 6,185 nuclear warheads. At its peak during the mid-1960s, the American nuclear arsenal consisted of more than 31,000 nuclear weapons.
NATO's changing strategies favored the use of nuclear weapons for purely defensive purposes, but according to some analysts, the Trump administration's policies mark an apparent departure from those standards. In 2018 Trump indicated his intent to start rebuilding the United States' nuclear stockpile as a means of discouraging possible international aggression by rival nuclear states including Russia and China. In late January 2020 media outlets reported that the United States military, under Trump's direction, had initiated its first deployment of a novel, compact type of nuclear warhead. American military officials did not initially confirm or deny the reports, but a US Navy officer later confirmed the reports and characterized the development as a necessary deterrent in an age of uncertainty.