World War III (WWIII orWW3), also known as theThird World War, is a hypothetical futureglobal conflict subsequent toWorld War I (1914–1918) andWorld War II (1939–1945). It is widely predicted that such a war would involve all of thegreat powers, like its two predecessors, and the potential use ofnuclear weapons or otherweapons of mass destruction, thereby surpassing all prior conflicts in scale, devastation, and loss of life.

Since theManhattan Project's development of nuclear weapons in 1945 and their use by theUnited States in theatomic bombings of Hiroshima and Nagasaki at the end of World War II, the risk of anuclear apocalypse causing widespread destruction and the potentialcollapse of modern civilization orhuman extinction has been a common theme in speculation and fiction about World War III. The risk of a third world war rose with the start of theCold War in 1947 and spread of nuclear weapons to theSoviet Union in 1949, which was followed by their acquisition byseveral other countries. The possibility was anticipated and planned for by military and civil personnel around the world, with scenarios ranging fromconventional warfare to limited or totalnuclear warfare. Regionalproxy wars including theKorean War (1950–1953),Vietnam War (1955–1975), andSoviet–Afghan War (1979–1989), while significant, did not lead to a full-scale global conflict. After events such as theCuban Missile Crisis in 1962, which brought the U.S. and Soviet Union to the brink of war, the strategic doctrine ofmutually assured destruction, which held that a full-scale nuclear war would annihilate all parties to the conflict, became widely accepted.

Since the end of the Cold War in 1991, speculation about World War III has shifted toward emerging threats, includingterrorism,cyberwarfare, and renewed great-power competition between the U.S.,China, andRussia. Various conflicts, most significantly theRussian invasion of Ukraine ongoing since 2022, as well as rising tensions over the status ofTaiwan, have been perceived as potential flashpoints or triggers for a third world war.^[1][2][3]

Time magazine was an early adopter, if not originator, of the term "World War III". The first usage appears in its 3 November 1941 issue (preceding the Japaneseattack on Pearl Harbor on 7 December 1941) under its "National Affairs" section and entitled "World War III?" aboutNazi refugeeHermann Rauschning, who had just arrived in the United States.^[4] In its 22 March 1943, issue under its "Foreign News" section,Time reused the same title "World War III?" about statements by then-US Vice PresidentHenry A. Wallace: "We shall decide sometime in 1943 or 1944 ... whether to plant the seeds of World War III."^[5][6]Time continued to entitle with or mention in stories the term "World War III" for the rest of the decade and onwards: 1944,^[7][8] 1945,^[9][10] 1946 ("bacterial warfare"),^[11] 1947,^[12] and 1948.^[13]Time persists in using this term, for example, in a 2015 book review entitled "This Is What World War III Will Look Like".^[14]

Military strategists have used war games to prepare for various war scenarios and to determine the most appropriate strategies. War games were utilized for World War I and World War II.^[15]

British Prime MinisterWinston Churchill was concerned that, with the enormous size of SovietRed Army forces deployed inCentral and Eastern Europe at theend of World War II and the unreliability of the Soviet leaderJoseph Stalin, there was a serious threat toWestern Europe. In April–May 1945, theBritish Armed Forces developedOperation Unthinkable, thought to be the first scenario of the Third World War.^[16] Its primary goal was "to impose upon Russia the will of the United States and theBritish Empire".^[17] The plan was rejected by the BritishChiefs of Staff Committee as militarily unfeasible.

Operation Dropshot was the 1950s United States contingency plan for a possiblenuclear and conventional war with theSoviet Union in the Western European and Asian theaters. Although the scenario made use of nuclear weapons, they were not expected to play a decisive role.

At the time, theUS nuclear arsenal was limited in size, based mostly in the United States, and depended onbombers for delivery. Dropshot included mission profiles that would have used 300nuclear bombs and 29,000 high-explosive bombs on 200 targets in 100 cities and towns to wipe out 85% of the Soviet Union's industrial potential in a single stroke. Between 75 and 100 of the 300 nuclear weapons were targeted to destroy Soviet combat aircraft on the ground.

The scenario was devised before the development ofintercontinental ballistic missiles. It was also devised beforeUS PresidentJohn F. Kennedy and hisSecretary of DefenseRobert McNamara changed the US Nuclear War plan from the 'city killing'countervalue strike plan to a "counterforce" plan (targeted more at military forces). Nuclear weapons at this time were not accurate enough to hit a naval base without destroying the city adjacent to it, so the aim of using them was to destroy the enemy's industrial capacity to cripple their war economy.

Ireland started planning for a possible nuclear war in the late 1940s. Co-operation between the United Kingdom and Ireland would be formed in the event of WWIII, where they would share weather data, control aids to navigation, and coordinate the Wartime Broadcasting Service that would occur after a nuclear attack.^[18]Operation Sandstone in Ireland was a top-secret British-Irish military operation.^[18] The armed forces from both states began a coastal survey of Britain and Ireland cooperating from 1948 to 1955. This was a request from the United States to identify suitable landing grounds for the US in the event of a successful Soviet invasion.^[18][19] By 1953, the co-operation agreed upon sharing information on wartime weather and the evacuation of civilian refugees from Britain to Ireland.^[18] Ireland's Operation Sandstone ended in 1966.^[19]

In January 1950, theNorth Atlantic Council approvedNATO's military strategy ofcontainment.^[20] NATO military planning took on a renewed urgency following the outbreak of theKorean War in the early 1950s, prompting NATO to establish a "force under a centralized command, adequate to deter aggression and to ensure the defense of Western Europe".Allied Command Europe was established underGeneral of the ArmyDwight D. Eisenhower,U.S. Army, on 2 April 1951.^[21][22] TheWestern Union Defence Organization had previously carried outExercise Verity, a 1949 multilateral exercise involving naval air strikes and submarine attacks.

Exercise Mainbrace brought together 200 ships and over 50,000 personnel to practice the defense ofDenmark andNorway from the Soviet attack in 1952. It was the first major NATO exercise. The exercise was jointly commanded bySupreme Allied Commander AtlanticAdmiralLynde D. McCormick,United States Navy, andSupreme Allied Commander EuropeGeneralMatthew B. Ridgeway,U.S. Army, during the autumn of 1952.

The United States, the United Kingdom,Canada,France, Denmark, Norway,Portugal,Netherlands, andBelgium participated.

Exercises Grand Slam and Longstep were naval exercises held in theMediterranean Sea during 1952 to practice dislodging an enemy occupying force and amphibious assault. It involved over 170 warships and 700 aircraft under the overall command of AdmiralRobert B. Carney. The overall exercise commander, Carney summarized the accomplishments of Exercise Grand Slam by stating: "We have demonstrated that the senior commanders of all four powers can successfully take charge of a mixed task force and handle it effectively as a working unit."^{[citation needed]}

The Soviet Union called the exercises "war-like acts" by NATO, with particular reference to the participation ofNorway and Denmark and prepared for its military maneuvers in theSoviet Zone.^[23][24]

Exercise Strikeback was a major NATO naval exercise held in 1957, simulating a response to an all-out Soviet attack on NATO. The exercise involved over 200 warships, 650 aircraft, and 75,000 personnel from theUnited States Navy, the United Kingdom'sRoyal Navy, theRoyal Canadian Navy, theFrench Navy, theRoyal Netherlands Navy, and theRoyal Norwegian Navy. As the largest peacetime naval operation up to that time, Exercise Strikeback was characterized by military analystHanson W. Baldwin ofThe New York Times as "constituting the strongest striking fleet assembled since World War II".^[25]

Exercise Reforger (from theREturn ofFORces toGERmany) was an annual exercise conducted during the Cold War byNATO. While US troops could be easily flown across the Atlantic, the heavy equipment and armor reinforcements would have to come by sea and be delivered to POMCUS (Pre-positioned Overseas Material Configured to Unit Sets) sites.^[26] These exercises tested the United States and allied abilities to carry out transcontinental reinforcement.^[26] Timely reinforcement was a critical part of the NATO reinforcement exercises. The United States needed to be able to send active-duty army divisions to Europe within ten days as part of a wartime NATO general deployment.^[26] In addition to assessing the capabilities of the United States, Reforger also monitored the personnel, facilities, and equipment of the European countries playing a significant role in the reinforcement effort.^[26] The exercise was intended to ensure that NATO could quickly deploy forces to West Germany in the event of a conflict with theWarsaw Pact. The Warsaw Pact outnumbered NATO throughout the Cold War in conventional forces, and especially in tanks and armoured vehicles. Therefore, in the event of a Soviet invasion, in order not to resort totactical nuclear strikes, NATO forces defending against aWarsaw Pactarmored spearhead would have to be quickly resupplied and replaced.

Reforger was not merely a show of force. In the event of a conflict, it would be the actual plan to strengthen the NATO presence in Europe.^{[citation needed]} In that instance, it would have been referred to as Operation Reforger. The political goals of Reforger were to promote extended deterrence and foster NATO cohesion.^[26] Important components in Reforger included theMilitary Airlift Command, theMilitary Sealift Command, and theCivil Reserve Air Fleet.

Seven Days to the River Rhine was a top-secret military simulation exercise developed in 1979 by the Warsaw Pact. It started with the assumption that NATO would launch a nuclear attack on theVistula river valley in a first-strike scenario, which would result in as many as two million Polish civilian casualties.^[27] In response, a Soviet counter-strike would be carried out againstWest Germany,Belgium, theNetherlands andDenmark, with Warsaw Pact forces invading West Germany and aiming to stop at theRiver Rhine by the seventh day. Other USSR plans stopped only upon reaching theFrench border on day nine. Individual Warsaw Pact states were only assigned their subpart of the strategic picture; in this case, the Polish forces were only expected to go as far as Germany. The Seven Days to the Rhine plan envisioned that Poland and Germany would be largely destroyed by nuclear exchanges and that large numbers of troops would die ofradiation sickness. It was estimated that NATO would fire nuclear weapons behind the advancing Soviet lines to cut off their supply lines and thus blunt their advance. While this plan assumed that NATO would use nuclear weapons to push back any Warsaw Pact invasion, it did not include nuclear strikes on France or the United Kingdom. Newspapers speculated when this plan was declassified, that France and the UK were not to be hit to get them to withhold the use of their nuclear weapons.

Exercise Able Archer was an annual exercise by theU.S. European Command that practiced command and control procedures, with emphasis on the transition from solely conventional operations to chemical, nuclear, and conventional operations during a time of war.

"Able Archer 83" was a five-dayNorth Atlantic Treaty Organization (NATO)command postexercise starting on 7 November 1983, that spannedWestern Europe, centered on theSupreme Headquarters Allied Powers Europe (SHAPE) Headquarters inCasteau, north of the city ofMons. Able Archer's exercises simulated a period ofconflict escalation, culminating in a coordinatednuclear attack.^[28]

The realistic nature of the 1983 exercise, coupled withdeteriorating relations between the United States and the Soviet Union and the anticipated arrival ofstrategicPershing II nuclear missiles in Europe, led some members of theSoviet Politburo and military to believe that Able Archer 83 was aruse of war, obscuring preparations for a genuine nuclear first strike.^{[28][29][30][31]} In response, the Soviets readied their nuclear forces and placed air units inEast Germany andPoland on alert.^[32][33]

This "1983 war scare" is considered by many historians to be the closest the world has come to nuclear war since theCuban Missile Crisis of 1962.^[34] The threat of nuclear war ended with the conclusion of the exercise on 11 November.^[35][36]

The Strategic Defense Initiative (SDI) was proposed by US PresidentRonald Reagan on 23 March 1983.^[37] In the latter part of hispresidency, numerous factors (which included watching the 1983 movieThe Day After and hearing through a Soviet defector thatAble Archer 83 almost triggered a Russian first strike) had turned Reagan against the concept of winnable nuclear war, and he began to see nuclear weapons as more of a "wild card" than a strategic deterrent. Although he later believed indisarmament treaties slowly blunting the danger of nuclear weaponry by reducing their number and alert status, he also believed a technological solution might allow incoming ICBMs to be shot down, thus making the US invulnerable to a first strike. However, the USSR saw the SDI concept as a major threat, since a unilateral deployment of the system would allow the US to launch a massive first strike on the Soviet Union without any fear of retaliation.

The SDI concept was to use ground-based and space-based systems to protect the United States from attack by strategicnuclearballistic missiles. The initiative focused on strategic defense rather than the prior strategic offense doctrine ofmutually assured destruction (MAD). The Strategic Defense Initiative Organization (SDIO) was set up in 1984 within theUnited States Department of Defense to oversee the Strategic Defense Initiative.

NATO operational plans for a Third World War have involved NATO allies who do not have their nuclear weapons, using nuclear weapons supplied by the United States as part of a general NATO war plan, under the direction of NATO'sSupreme Allied Commander.

Of the three nuclear powers in NATO (France, the United Kingdom, and the United States), only the United States has provided weapons for nuclear sharing. As of November 2009^[update],Belgium,Germany,Italy, theNetherlands andTurkey are still hosting US nuclear weapons as part of NATO's nuclear sharing policy.^[38][39]Canada hosted weapons until 1984,^[40] andGreece until 2001.^[38][41] TheUnited Kingdom also received US tactical nuclear weapons such asnuclear artillery andLance missiles until 1992, despite the UK being anuclear weapons state in its own right; these were mainly deployed inGermany.

Inpeacetime, the nuclear weapons stored in non-nuclear countries are guarded byUS airmen though previously some artillery and missile systems were guarded by US Army soldiers; the codes required for detonating them are under American control. In case of war, the weapons are to be mounted on the participating countries' warplanes. The weapons are under custody and control ofUSAF Munitions Support Squadrons co-located on NATO main operating bases that work together with the host nation forces.^[38]

As of 2005,^[update] 180 tacticalB61 nuclear bombs of the 480 US nuclear weapons believed to be deployed in Europe fall under the nuclear sharing arrangement.^[42] The weapons are stored within a vault inhardened aircraft shelters, using theUSAFWS3 Weapon Storage and Security System. The delivery warplanes used areF-16 Fighting Falcons andPanavia Tornados.^[43]

With the initiation of theCold Wararms race in the 1950s, anapocalyptic war between the United States and the Soviet Union became a real possibility. During the Cold War era (1947–1991), several military events have been described as having come close to potentially triggering World War III. Even after the end of the Cold War and the dissolution of the Soviet Union in 1991, some incidents afterward have been described as close calls as well.

TheKorean War was a war between two coalitions fighting for control over theKorean Peninsula: a communist coalition includingNorth Korea, the People's Republic of China, and theSoviet Union, and a capitalist coalition includingSouth Korea, the United States and theUnited Nations Command. Many then believed that the conflict was likely to soon escalate into a full-scale war between the three countries, the U.S., the U.S.S.R., and China.CBS News war correspondentBill Downs wrote in 1951, "To my mind, the answer is: Yes, Korea is the beginning of World War III. The brilliantlandings at Inchon and the cooperative efforts of theAmerican armed forces with theUnited Nations Allies have won us a victory in Korea. But this is only the first battle in a major international struggle which now is engulfing the Far East and the entire world."^[44] Downs afterwards repeated this belief onABC Evening News while reporting on theUSSPueblo incident in 1968.^[45] Secretary of StateDean Acheson later acknowledged that theTruman administration was concerned about the escalation of the conflict and that GeneralDouglas MacArthur warned him that a U.S.-led intervention risked a Soviet response.^[46]

TheBerlin Crisis of 1961 was a political-military confrontation between the armed forces of the U.S. and the U.S.S.R. atCheckpoint Charlie with both several American and Soviet/East German tanks and troops at the stand-off at each other only 100 yards on either side of the checkpoint. The reason behind the confrontation was the occupational status of the German capital city,Berlin, and ofpost–World War II Germany. The Berlin Crisis started when the USSR launched an ultimatum demanding the withdrawal of all armed forces from Berlin, including the Western armed forces inWest Berlin. The crisis culminated in the city's de facto partition with theEast German erection of theBerlin Wall. This stand-off ended peacefully on 28 October following a U.S.–Soviet understanding to withdraw tanks and reduce tensions.

TheCuban Missile Crisis, a confrontation on the stationing of Soviet nuclear missiles in Cuba in response to the failedBay of Pigs Invasion, is considered as having been the closest to a nuclear exchange, which could have precipitated a third World War.^[47] The crisis peaked on 27 October, with three separate major incidents occurring on the same day:

• The most critical incident occurred when a Soviet submarine nearly launched anuclear-tipped torpedo in response to having been targeted by American navaldepth charges in international waters, with the Soviet nuclear launch response only having been prevented bySoviet Navy executive officerVasily Arkhipov.
• The shooting down of aLockheed U-2 spy plane piloted byRudolf Anderson while violating Cuban airspace.
• The near interception of another U-2 that had strayed into Soviet airspace overSiberia, which airspace violation nearly caused the Soviets to believe that this might be the vanguard of a US aerial bombardment.

Despite what many believe to be the closest the world has come to a nuclear conflict, throughout the entire standoff, theDoomsday Clock, which is run by theBulletin of the Atomic Scientists to estimate how close the end of the world, or doomsday, is, with midnight being the apocalypse, stayed at a relatively stable seven minutes to midnight. This has been explained as being due to the brevity of the crisis since the clock monitored more long-term factors such as the leadership of countries, conflicts, wars, and political upheavals, as well as societies' reactions to said factors.

TheBulletin of the Atomic Scientists now credits the political developments resulting from the Cuban Missile Crisis with having enhanced global stability. TheBulletin posits that future crises and occasions that might otherwise escalate, were rendered more stable due to two major factors:

1. AWashington to Moscow hotline resulted from the communication trouble between theWhite House and theKremlin during the crisis. This gave the leaders of the two largest nuclear powers the ability to contact each other in real-time, vital when seconds could potentially prevent a nuclear exchange.
2. The second factor was caused in part due to the worldwide reaction to how close the US and USSR had come to the brink of World War III during the standoff. As the public began to more closely monitor topics involving nuclear weapons, and therefore to rally support for the cause of non-proliferation, the1963 test ban treaty was signed. To date this treaty has been signed by 126 total nations, with the most notable exceptions beingFrance andChina. Both of these countries were still in the relative beginning stages of their nuclear programs at the time of the original treaty signing, and both sought nuclear capabilities independent of their allies. This Test Ban Treaty prevented the testing of nuclear ordnance that detonated in theatmosphere, limitingnuclear weapons testing to below ground and underwater, decreasingfallout and effects on the environment, and subsequently caused the Doomsday Clock to decrease by five minutes, to arrive at a total of twelve minutes to midnight.^[48] Up until this point, over 1000 nuclear bombs had been detonated, and concerns over both long and short term effects to the planet became increasingly more worrisome to scientists.

TheSino-Soviet border conflict was a seven-month undeclared military border war between theSoviet Union andChina at the height of theSino-Soviet split in 1969. The most serious of these border clashes, which brought the world's two largestcommunist states to the brink of war, occurred in March 1969 in the vicinity ofZhenbao (Damansky) Island on theUssuri (Wusuli) River, nearManchuria.

The conflict resulted in a ceasefire, with a return to the status quo. Critics point out that the Chinese attack on Zhenbao was to deter any potential future Soviet invasions; that by killing some Soviets, China demonstrated that it could not be 'bullied'; and that Mao wanted to teach them 'a bitter lesson'.

China's relations with the USSR remained sour after the conflict, despite the border talks, which began in 1969 and continued inconclusively for a decade. Domestically, the threat of war caused by the border clashes inaugurated a new stage in theCultural Revolution; that of China's thorough militarization. The9th National Congress of the Chinese Communist Party, held in the aftermath of theZhenbao Island incident, confirmed Defense MinisterLin Biao asMao Zedong's heir apparent.

Following the events of 1969, the Soviet Union further increased itsforces along theSino-Soviet border, and in theMongolian People's Republic.

TheYom Kippur War, also known as the Ramadan War, or October War, began with a surprise invasion ofIsraeli-occupied territories by a coalition of Arab states, aided by the Soviet Union. Israel successfully counterattacked with the aid of the US. Tensions grew between the two superpowers: American and Soviet naval forces came close to firing upon each other in theMediterranean Sea. AdmiralDaniel J. Murphy of theUS Sixth Fleet reckoned the chances of the Soviet squadron attempting a first strike against his fleet at 40 percent. The Pentagon moved Defcon status from 4 to 3.^[49] The superpowers had been pushed to the brink of war, but tensions eased with the ceasefire brought in underUNSC 339.^[50][51]

The United States made emergency retaliation preparations afterNORAD systems indicated that a full-scale Soviet attack had been launched.^[52] No attempt was made to use theMoscow–Washington hotline to clarify the situation with the USSR and it was not until early-warning radar systems confirmed no such launch had taken place that NORAD realized that a computer system test had caused the display errors. A senator inside the NORAD facility at the time described an atmosphere of absolute panic. A GAO investigation led to the construction of an off-site test facility to prevent similar mistakes.^[53]

A false alarm occurred on theSoviet nuclear early warning system, showing the launch of AmericanLGM-30 Minutemanintercontinental ballistic missiles from bases in the United States. A retaliatory attack was prevented byStanislav Petrov, aSoviet Air Defence Forces officer, who realised the system had simply malfunctioned (which was borne out by later investigations).^[54][55]

DuringAble Archer 83, a ten-dayNATO exercise simulating a period ofconflict escalation that culminated in aDEFCON 1 nuclear strike, some members of theSovietPolitburo andarmed forces treated the events as aruse of war concealing a genuine first strike. In response, the military prepared for a coordinated counter-attack by readying nuclear forces and placing air units stationed in theWarsaw Pact states ofEast Germany andPoland under high alert. However, the state of Soviet preparation for retaliation ceased upon completion of the Able Archer exercises.^[28]

TheNorwegian rocket incident was the first World War III close call to occur after the Cold War had ended. This incident occurred when Russia'sOlenegorskearly warning station accidentally mistook the radar signature from aBlack Brant XIIresearch rocket (being jointly launched by Norwegian and US scientists fromAndøya Rocket Range), as appearing to be the radar signature of the launch of aTridentSLBM missile. In response,Russian PresidentBoris Yeltsin was summoned and theChegetnuclear briefcase was activated for the first and only time. However, the high command was soon able to determine that the rocket was not entering Russian airspace, and promptly aborted plans for combat readiness and retaliation. It was retrospectively determined that, while the rocket scientists had informed thirty states including Russia about the test launch, the information had not reached Russian radar technicians.^[56][57]

On 12 June 1999, the day following the end of theKosovo War, some 250 Russian peacekeepers occupied thePristina International Airport ahead of the arrival ofNATO troops and were to secure the arrival of reinforcements by air. American NATO Supreme Allied Commander Europe GeneralWesley Clark ordered the use of force against the Russians.^[58]Mike Jackson, aBritish Army general who contacted the Russians during the incident, refused to enforce Clark's orders, famously telling him "I'm not going to start the Third World War for you".^[59] CaptainJames Blunt, the lead officer at the front of the NATO column in the direct armed stand-off against the Russians, received the "Destroy!" orders from Clark over the radio, but he followed Jackson's orders to encircle the airfield instead and later said in an interview that even without Jackson's intervention he would have refused to follow Clark's order.^[60]

On 24 November 2015, at the border between Turkey and Syria, theTurkish Air Force shot down a RussianSukhoi attack aircraft. The Turks claimed that the aircraft violated Turkishairspace, a claim denied by the Russians; the plane was in the region as part of theRussian military intervention in the Syrian civil war, in which Turkey supported opposing forces. The incident was the first destruction of aRussian orSoviet Air Forces warplane by aNATO member state since theattack on the Sui-ho Dam during the Korean War in 1953.^[61][62] The incident led to numerous media and individuals commenting that it could have sparked and escalated into a world war.^[63][64][65]

On 24 February 2022, Russia's presidentVladimir Putin ordered a full-scale invasion ofUkraine, marking a major escalation of theRusso-Ukrainian War, which began in 2014. The Russian invasion started the largest war in Europe since World War II.^[66] Various experts, analysts, and others have described the invasion as heightening the risk of a third world war,^{[67][68][69][70]} while others have suggested the contrary.^[71][72][73]

Because of the invasion, at least fifty countries have provided some kind ofmilitary aid to Ukraine, including allmember states of NATO.^[74][75] The Russian government has threatened retaliation against countries supplying military aid to Ukraine, and said it meant NATO was waging a "proxy war" against Russia.^[76] Senior Russian politicians—including president Putin, foreign ministerSergey Lavrov andUnited Russia party leaderDmitry Medvedev—have made statements widely seen asnuclear blackmail. They have implied that Russia may use nuclear weapons if certain"red lines" are crossed, such as helping Ukraine to strike back at mainland Russia.^[77][78][79] Officials from the United States and NATO, including US presidentJoe Biden and NATO secretary generalJens Stoltenberg, have stressed the need to prevent the conflict escalating into a third world war, while also affirming that NATO members will defend each other.^{[80][81][82][83]} The US warned Russia's government that the country would suffer "catastrophic" consequences if it used nuclear weapons against Ukraine.^[84][85] FormerCIA Director,David Petraeus, said NATO would likely respond by destroying all Russian forces in Ukraine.^[86] Several incidents have risked a direct conflict between Russia and NATO, such asRussian breaches of NATO airspace anda missile explosion in Poland.^[87][88][89] In early 2023, Putin suspended Russia's participation inNew START, the last remaining nuclear treaty between Russia and the US,^[90] and announced plans to install Russian tactical nuclear weapons inBelarus.^[91]

Russian threats have been described as a way to intimidate Western countries, to deter them from helping Ukraine.^[92] Fearing escalation, NATO countries held back from sending advanced weapons to Ukraine, and forbade Ukraine to fire NATO weapons into Russia.^[93] Since July 2024, they have allowed Ukraine to use NATO weapons to strike military targets in Russia, but only near the border in self-defense.^[94] Russia's government has not followed through on its threats against NATO and has not used nuclear weapons, despite most of its "red lines" being crossed.^[95]

Iran andNorth Korea have provided weapons and ammunition to Russia during the invasion, including ballistic missiles.^[96] In 2024, Russia and North Korea signed adefense pact, and that November, Russia further escalated the conflict by deploying 10,000 North Korean troops on its border to fight Ukraine.^[97] In November 2024, Putin said that the war "has acquired elements of a global character", adding that Russia was entitled to strike military facilities of those countries that allow their weapons to be used against mainland Russia.^[98]

In February 2025, U.S. PresidentDonald Trump, his Vice PresidentJD Vance, and Ukrainian PresidentVolodymyr Zelenskyy met to discuss signing an agreement for U.S. access to Ukrainian oil, gas, and rare earths. During the meeting, an argument erupted, with President Trump at one point chiding Zelenskyy for not being grateful enough for U.S. military and political support for Ukraine during the war, telling him he was "gambling with World War Three."^[99] The agreements were not signed, and Trump later said that Zelenskyy "is not ready for peace if America is involved because he feels our involvement gives him a big advantage in negotiations."^[100]Currently the two forces, Russia and Ukraine, are considering a 30-day ceasefire.

As Soviet-American relations grew tense in the post-World War II period, the fear that the tension could escalate into World War III was ever-present. AGallup poll in December 1950 found that more than half of Americans considered World War III to have already started.^[101]

In 2004, commentatorNorman Podhoretz proposed that theCold War, lasting from the surrender of theAxis powers until thefall of the Berlin Wall, might rightly be called World War III. By Podhoretz's reckoning, "World War IV" would be the global campaign againstIslamofascism.^[102][103]

Still, the majority of historians would seem to hold that World War III would necessarily have to be a worldwide "war in which large forces from many countries fought"^[104] and a war that "involves most of the principal nations of the world".^[105] The Cold War received its name from the lack of action taken from both sides. The lack of action was out of fear that a nuclear war would possibly destroy humanity.^[106] In his bookSecret Weapons of the Cold War, Bill Yenne concludes that the militarySuperpower standoff from the 1940s through to 1991, was not World War III.^[107]

The "war on terror" that began with theSeptember 11 attacks has been claimed by some to be World War III^[108] or sometimes World War IV^[102][109] (assuming the Cold War was World War III). Others have disparaged such claims as "distortingAmerican history". While there is general agreement amongst historians regarding the definitions and extent of the first two world wars, namely due to the unmistakable global scale of aggression and self-destruction of these two wars, a few have claimed that a "World War" might now no longer require such worldwide and large-scale aggression and carnage. Still, such claims of a new "lower threshold of aggression", that might now be sufficient to qualify a war as a "World War" have not gained such widespread acceptance and support as the definitions of the first two world wars have received amongst historians.^[110]

On 1 February 2015,Iraqi Foreign MinisterIbrahim al-Jaafari declared that thewar against the Islamic State was effectively "World War III", due to the Islamic State's aims for a worldwide caliphate, and its success in spreading the conflict to multiple countries outside of theLevant region.^[111] In response to theNovember 2015 Paris attacks,King of JordanAbdullah II stated "We are facing a Third World War [withinIslam]".^[112]

In hisState of the Union Address on 12 January 2016, US PresidentBarack Obama warned that news reports granting ISIL the supposed ability to foment a third World War might be excessive and irresponsible, stating that "as we focus on destroying ISIL, over-the-top claims that this is World War III just play into their hands. Masses of fighters on the back of pickup trucks and twisted souls plotting in apartments or garages pose an enormous danger to civilians and must be stopped. But they do not threaten our national existence."^[113]

In multiple recorded interviews under somewhat casual circumstances, comparing the conflagrations of World War I and II to the ongoing lower-intensity wars of the 21st century,Pope Francis has said, "The world is at war because it has lost the peace", and "perhaps one can speak of a third war, one fought piecemeal".^[114][115]

In 1949, after the unleashing of nuclear weaponry at the end of World War II, physicistAlbert Einstein suggested that any outcome of a possible World War III would be so catastrophic uponhuman civilization so as to revert mankind to theStone 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".^[116][117]

As for theextermination of the human race as aconsequence 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."^[118]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, according to Brinton.^[119]James Burnham of theOffice of Strategic Services (the precursor to theCIA), 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.^[120]

A 1998New 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".^[121] In particular, theUnited 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 aretaliatory launch due to a false warning, similar to the 1983 incident.^[121] 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 theRussian invasion of Ukraine,Chinese expansion into adjacent islands and seas,^[1]Sino-Indian border dispute,Chinese threats of military operation against Taiwan,Indo-Pakistani wars border conflicts, andforeign involvement in the Syrian civil war. Other hypothesized risks are that a war involving or betweenSaudi Arabia andIran,Israel and Iran,United States and Iran,India andPakistan,Ukraine andRussia,Poland andBelarus,South Korea andNorth Korea, orTaiwan andChina 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 alliancesNATO andCSTO, or even the possibility of a "rogue commander" under any nuclear power might launch an unauthorized strike that escalates into a full-blown war.^[122]

According to a peer-reviewed study published in the journalNature 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 bystarvation during anuclear winter. More than two billion people could die of starvation from a smaller-scale (5–47 Tg) nuclear war between India and Pakistan.^[123][124] 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.^[125]

Some scenarios involve risks due to upcoming changes from the known status quo. In the 1980s theStrategic Defense Initiative made an effort at nullifying the USSR's nuclear arsenal; some analysts believe the initiative was "destabilizing".^[126][127] In his bookDestined for War,Graham Allison views the global rivalry between the established power, the US, and the rising power, China, as an example of theThucydides Trap. Allison states that historically, "12 of 16 past cases where a rising power has confronted a ruling power" have led to fighting.^[128] In 2020 and 2023, theBulletin of the Atomic Scientists advanced its Doomsday Clock, citing among other factors a predicted destabilizing effect from upcominghypersonic weapons.^[129]

Emerging technologies, such asartificial intelligence, could hypothetically generate risk in the decades ahead. A 2018RAND 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 anadversarial exploitation of such an AI's algorithms by a third party to trigger a launch recommendation.^[130][131] 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.^[132]

Cyberwarfare 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.^[133][134] There has been a proliferation of state-sponsored attacks. The trends of these attacks suggest the potential of a cyber World War III.^[134] 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.^[134] The2022 Russian invasion of Ukraine has sparked concerns about a large-scalecyberattack, 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.^[135] Russia's use of cyberwarfare has turned the war into a large-scale "hybrid" war in Ukraine.^[135]

• Anti-nuclear movement
• Artificial intelligence arms race
• Artificial Intelligence Cold War
• Global catastrophe scenarios
• Nuclear arms race
• Nuclear holocaust
• Nuclear terrorism
• Second Cold War
• World War III in popular culture
• War

• Huntington, Samuel (1996).The Clash of Civilizations and the Remaking of World Order Simon & Schuster, New York.ISBN 978-0-684-84441-1.
• Langford, David (1981).War in 2080 : the future of military technology. London: Sphere Books.ISBN 978-0-7221-5393-2.
• Mearsheimer, John (2001).The Tragedy of Great Power Politics. W. W. Norton, New York.ISBN 978-0-393-34927-6.
• Pamidi, G.G. (2012).Possibility of a nuclear war in Asia : an Indian perspective. New Delhi: United Service Institution of India : Vij Books India.ISBN 978-93-81411-51-3.
• Piepers, Ingo (2016).2020: WARning. Conijn Advies.ISBN 978-90-824118-1-2.