World War III

Due to the development of nuclear weapons in the Manhattan Project, which were used in the atomic bombings of Hiroshima and Nagasaki near the end of World War II, and their subsequent acquisition and deployment by many countries afterward, the potential risk of a nuclear apocalypse causing inevitable widespread mass destruction of Earth's civilizations and life is a common theme in speculations about a third world war. Another primary concern is that biological warfare could cause mass casualties. It could happen intentionally or inadvertently, by an accidental release of a biological agent, the unexpected mutation of an agent, or its adaptation to other species after use. Large-scale apocalyptic events like these, caused by advanced technology used for destruction, could render most of Earth's surface uninhabitable.


Before the beginning of World War II in 1939, World War I (1914–1918) was believed to have been "the war to end all wars". It was popularly believed that never again could there possibly be a global conflict of such magnitude. During the interwar period, World War I was typically referred to simply as "The Great War". The outbreak of World War II disproved the hope that humanity might have "outgrown" the need for widespread global wars.^[3]


With the advent of the Cold War in 1947 and the spread of nuclear weapons and technology to the Soviet Union, the possibility of a third global conflict increased. During the Cold War, the possibility of a third world war was anticipated and planned for by military and civil personnel in various countries. Scenarios ranged from conventional warfare to limited or total nuclear warfare. At the height of the Cold War, the doctrine of mutually assured destruction (MAD), which determined that an all-out nuclear confrontation would destroy all of the states involved in the conflict, developed. The potential for the absolute destruction of the human species may have contributed to both American and Soviet leaders avoiding such a scenario.


The various global military conflicts that have occurred since the start of the 21st century, most recently the Syrian civil war since 2011, the Russian invasion of Ukraine since 2022, and the Israel–Hamas war since 2023, alongside recent rising tensions between the United States and China, have been perceived as potential flashpoints or triggers for a third world war.^[4][5]

Hypothetical scenarios

In 1949, after the unleashing of nuclear weaponry at the end of World War II, physicist Albert Einstein suggested that any outcome of a possible World War III would be so dire as to revert mankind to the Stone Age. When asked by journalist Alfred Werner what types of weapons Einstein believed World War III might be fought with, Einstein warned, "I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones".^[2][104]


As for the extermination of the human race as a consequence of atomic war, Leslie A. White challenged Einstein, "this too may be admitted as possibility, and all we can say is that if it is to come, it will come. Extravagant expressions of horror will not alter the course of events."^[105] Crane Brinton also doubted the psychological pacification of Einstein: "Teachers, preachers, educators, even politicians are telling the growing generation that there must be no war and, therefore, there will be no war. I have doubts as to whether this is wise teaching…" In spite of the atomic bomb, there will be another general war and humanity will survive it.^[106] James Burnham of Office of Strategic Services (the precursor of CIA), also believed in survival: The uniqueness of the atomic weapons is commonly found in that they can totally annihilate human life, including through climatic and geological chain reaction, but such is not the case. The great principles of military strategy stand unaltered. An atomic war will look different from older wars but it will be decided by the same combination of resources, morale and strategy.^[107]


A 1998 New England Journal of Medicine overview found that "Although many people believe that the threat of a nuclear attack largely disappeared with the end of the Cold War, there is considerable evidence to the contrary".^[108] In particular, the United States–Russia mutual detargeting agreement in 1994 was largely symbolic and did not change the amount of time required to launch an attack. The most likely "accidental-attack" scenario was believed to be a retaliatory launch due to a false warning, similar to the 1983 incident.^[108] Historically, World War I happened through an escalating crisis; World War II happened through deliberate action. Hypothesized flashpoints in the 2010s and the 2020s include the Russian invasion of Ukraine, Chinese expansion into adjacent islands and seas,^[4] Sino-Indian border dispute, Chinese threats of military operation against Taiwan, Indian—Pakistani border conflicts, and foreign involvement in the Syrian civil war. Other hypothesized risks are that a war involving or between Saudi Arabia and Iran, Israel and Iran, United States and Iran, India and Pakistan, Ukraine and Russia, Poland and Belarus, South Korea and North Korea, or Taiwan and China could escalate via alliances or intervention into a war between "great powers" such as the United States, United Kingdom, France, Germany, Russia, China, India, Japan or an all out war between military alliances NATO and CSTO, or even the possibility of a "rogue commander" under any nuclear power might launch an unauthorized strike that escalates into a full-blown war.^[109]


According to a peer-reviewed study published in the journal Nature Food in August 2022, a full-scale nuclear war between the United States and Russia, releasing over 150 Tg of stratospheric soot, could indirectly kill more than five billion people by starvation during a nuclear winter. More than two billion people could die of starvation from a smaller-scale (5–47 Tg) nuclear war between India and Pakistan.^[110][111] In the event of a nuclear war between Russia and the United States, 99% of the population in the belligerent countries, as well as Europe and China, would die.^[112]


Some scenarios involve risks due to upcoming changes from the known status quo. In the 1980s the Strategic Defense Initiative made an effort at nullifying the USSR's nuclear arsenal; some analysts believe the initiative was "destabilizing".^[113][114] In his book Destined for War, Graham Allison views the global rivalry between the established power, the US, and the rising power, China, as an example of the Thucydides Trap. Allison states that historically, "12 of 16 past cases where a rising power has confronted a ruling power" have led to fighting.^[115] In 2020 and 2023, the Bulletin of the Atomic Scientists advanced its Doomsday Clock, citing among other factors a predicted destabilizing effect from upcoming hypersonic weapons.^[116]


Emerging technologies, such as artificial intelligence, could hypothetically generate risk in the decades ahead. A 2018 RAND Corporation report has argued that AI and associated information technology "will have a large effect on nuclear-security issues in the next quarter century". A hypothetical future AI could provide a destabilizing ability to track "second-launch" launchers. Incorporating AI into decision support systems used to decide whether to launch, could also generate new risks, including the risk of an adversarial exploitation of such an AI's algorithms by a third party to trigger a launch recommendation.^[117][118] A perception that some sort of emerging technology would lead to "world domination" might also be destabilizing, for example by leading to fear of a pre-emptive strike.^[119]


Cyber warfare is the exploitation of technology by a nation-state or international organization to attack and destroy the opposing nation's information networks and computers. The damage can be caused by computer viruses or denial-of-service attacks (DoS). Cyberattacks are becoming increasingly common, threatening cybersecurity and making it a global priority.^[120][121] There has been a proliferation of state-sponsored attacks. The trends of these attacks suggest the potential of a cyber World War III.^[121] The world's leading militaries are developing cyber strategies, including ways to alter the enemy's command and control systems, early warning systems, logistics, and transportation.^[121] The 2022 Russian invasion of Ukraine has sparked concerns about a large-scale cyberattack, with Russia having previously launched cyberattacks to compromise organizations across Ukraine. Nearly 40 discrete attacks were launched by Russia which permanently destroyed files in hundreds of systems across dozens of organizations, with 40% aimed at critical infrastructure sectors in Ukraine.^[122] Russia's use of cyberwarfare has turned the war into a large-scale "hybrid" war in Ukraine.^[122]