Probability of an Underwater Nuclear Explosion amid China–Taiwan Tensions (2025
Rising Geopolitical and Military Tensions
Tensions between China and Taiwan have been escalating due to Beijing’s insistence on unification and Taipei’s resistance. China’s leadership (under President Xi Jinping) views Taiwan as a “core interest” and has not renounced the use of force to achieve unification chinapower.csis.org. In recent years, the People’s Liberation Army (PLA) has intensified military pressure on Taiwan. This has included almost daily incursions of Chinese fighter jets and bombers into Taiwan’s air defense identification zone, cyber attacks, and large-scale drills near Taiwan’s airspace and waters apln.network. Notably, after political developments such as high-level US visits in 2022 and Taiwan’s presidential election in January 2024 (which was won by a pro-independence-leaning party), Beijing staged live-fire exercises around the island as shows of force. In April 2024, the PLA even encircled Taiwan with an aircraft carrier group during drills intended to “warn” the new administration in Taipei armedservices.house.gov.
These actions underscore the heightened geopolitical stakes. The United States has reinforced its support for Taiwan through arms sales and statements of commitment to help defend the island, even as it maintains “strategic ambiguity” (not explicitly stating if it would intervene militarily) warontherocks.com. Meanwhile, China accuses Washington of encouraging “Taiwan independence” and has sought to deter U.S. involvement. This great-power rivalry over Taiwan raises the risk of miscalculation. Experts note that political tensions between Beijing and Taipei, combined with deepening U.S.-China strategic distrust, create a volatile backdrop where a crisis could “suddenly ignite” into conflict focustaiwan. tw apln.network.
Naval Activity and Nuclear Posturing
A Chinese Navy guided-missile destroyer (left) shadowing a Taiwanese warship during PLA exercises near Taiwan in May 2024 (photo courtesy of Taiwan’s Ministry of National Defense). Such naval drills demonstrate Beijing’s increasing capability to project power around the island.
China’s military buildup is especially evident at sea. The PLA Navy now conducts regular joint naval-air exercises in the Taiwan Strait and surrounding waters. In the past year, China even carried out a dual aircraft carrier exercise in the South China Sea – the first of its kind – showcasing a growing ability to coordinate blockade operations against Taiwan armedservices.house.gov. Dozens of warships, including advanced destroyers and coast guard vessels, have patrolled near Taiwan’s coast as part of “blockade” simulations warontherocks.com. These maneuvers underscore China’s preparation for a possible maritime siege or invasion scenario.
At the same time, nuclear posturing has subtly entered the equation. China has historically maintained a relatively modest nuclear arsenal and a declared No First Use (NFU) policy (pledging not to use nuclear weapons unless attacked with them first). Beijing’s official stance limits overt nuclear threats in the Taiwan context. However, China’s rapid nuclear modernization is changing the strategic picture. The U.S. Department of Defense reported that by late 2024 China had produced over 600 operational nuclear warheads, nearly tripling its stockpile since 2020 warontherocks.com. It is also diversifying its delivery systems – deploying ballistic missile submarines, introducing air-launched nuclear-capable missiles on H-6 bombers, and fielding new intermediate-range missiles that could carry nuclear or conventional warheads warontherocks.com. This buildup suggests Beijing is striving for a more robust deterrent and perhaps greater leverage in a high-stakes conflict.
Although Chinese officials do not explicitly threaten to use nuclear weapons over Taiwan, they are undoubtedly “leveraging [their] expanding nuclear arsenal” to caution the U.S. against intervening warontherocks.com. Chinese strategic writings discuss “strategic deterrence” – using all means (cyber attacks, space weapons, and the specter of nuclear escalation) to convince the U.S. that defending Taiwan would be too costly warontherocks.com. In a crisis, China might increase the readiness of its nuclear forces or signal its resolve (for example, by moving ballistic missile submarines into the Pacific or conducting missile test launches) as implicit nuclear posturing. Indeed, one analysis argues that any future Taiwan crisis “will almost certainly involve nuclear threats”, despite China’s NFU pledge, due to Beijing’s growing ability to brandish its nukes as a deterrent factor usni.org. Importantly, however, threats or alerts are very different from actual use. So far, Beijing has not indicated any intention to abandon its NFU doctrine, and it has not changed its nuclear policy even as the arsenal grows chinapower.csis.org. This implies that China still sees nuclear weapons primarily as political deterrents, not as tools for initiating war.
Expert Assessments of Nuclear Escalation Risk
The prospect of a war over Taiwan has drawn serious concern from international security experts. Each year since 2020, the Council on Foreign Relations (CFR) has ranked a China–Taiwan conflict as a top-tier geopolitical risk. In its latest Preventive Priorities Survey 2025, foreign policy experts rated a Taiwan Strait clash as having a “moderate” likelihood of occurring in the next year – but with a “high impact” given the potential to draw in the U.S. and other regional powers focustaiwan.tw. This underscores that while an outbreak of hostilities is not assured, it is considered a real possibility that policymakers must watch closely.
What about the risk of nuclear escalation in such a conflict? Most analysts still assess the probability of nuclear weapons being used as very low, but not zero. Notably, a 2023 survey by CSIS’s ChinaPower project revealed a striking perception gap: 44% of U.S. security experts believed China might be willing to detonate a nuclear weapon against U.S. or allied forces in a Taiwan war, whereas only 11% of experts in Taiwan thought China would go that far chinapower.csis.org. In other words, American experts are more wary that Beijing could resort to nukes if losing a war, while Taiwanese experts overwhelmingly (89%) judge that China “would not resort to using nuclear weapons” in a cross-strait conflict chinapower.csis.org. The consensus view in Taiwan – and among many international scholars – is that nuclear use would occur only under the most extreme circumstances apln.network. Beijing would have to feel an existential threat to the regime or homeland (for example, facing massive U.S. attacks on mainland cities or the imminent loss of its military) before considering such a drastic step.
Defense think tanks and wargame simulations generally reinforce the notion that nuclear escalation is highly unlikely in a Taiwan scenario. Wargames conducted by U.S. analysts (e.g. at CSIS and RAND) typically assume both China and the U.S. are extremely reluctant to cross the nuclear threshold, given the mutually catastrophic consequences. Unlike some Cold War scenarios, a conflict over Taiwan does not inherently require nuclear strikes to achieve military aims – and using one could backfire disastrously. As one scholarly analysis put it, “the use of nuclear weapons in the Taiwan Strait would happen only under extreme circumstances”, and even then it would be a desperate last resort tandfonline.com.
At the same time, experts caution that the risk is not zero and may be slowly rising. Several key factors could increase the danger of nuclear escalation in a U.S.-China war over Taiwan:
Intense Political and Great-Power Rivalry: The ideological and nationalistic stakes for Beijing (preventing Taiwan’s permanent separation) and for Washington (upholding its credibility and alliances) mean both sides would feel immense pressure to prevail apln.networkapln.network. This raises the temptation to “amp up” threats or escalation if one side is on the brink of defeat.
Shifting Military Balances: China’s growing conventional strength versus Taiwan (and its improving ability to threaten U.S. forces in Asia) might create incentives for escalation. If China’s invasion faltered against U.S. intervention, leaders might consider unconventional means to tilt the balance apln.network. Conversely, if U.S. forces struck deep into China (to neutralize the invasion), Beijing could see this as existential and contemplate its nuclear options.
Conventional-Nuclear Entanglement: Modern military systems are often dual-use. For instance, China’s conventional missiles and nuclear missiles may use similar launchers, or its command-and-control networks for conventional operations overlap with nuclear C2 apln.network. In the fog of war, strikes on certain targets or misinterpretation of an incoming attack could lead a side to mistakenly believe the other has gone nuclear, prompting a retaliatory escalation.
Poor Crisis Communication: Unlike U.S.-Soviet hotline protocols of the Cold War, today’s U.S.-China military dialogues are limited and “brittle” apln.network. During a fast-moving conflict, miscommunication or an inability to signal restraint could let an incident spiral. For example, if a Chinese ballistic-missile submarine were sunk (not knowing if it carried nuclear missiles), China’s leadership might panic about its deterrent and consider an extreme response. Robust communication channels are lacking, heightening miscalculation risks.
Despite these worrisome factors, most authorities still judge that nuclear use can be avoided. China has strong strategic reasons to avoid crossing the nuclear threshold in a Taiwan war, and the United States likewise has every incentive to prevent nuclear escalation. Both countries know that any nuclear exchange could quickly expand beyond control, resulting in unthinkable devastation for all parties.
China’s Nuclear Policy and Recent Developments
China’s official nuclear doctrine plays a crucial role in shaping the probability of a nuclear incident. Since its first nuclear test in 1964, the People’s Republic of China has maintained a policy of No First Use (NFU), pledging not to use nuclear weapons unless China itself is attacked with nuclear arms. Chinese leaders frequently reaffirm this NFU stance in international forums. Adhering to NFU means that, in theory, China would not initiate a nuclear strike over Taiwan or any other issue. This policy is a significant reassurance that constrains nuclear risk – as long as Beijing continues to honor it.
However, questions remain about how strictly NFU would hold in an actual war for Taiwan. China’s rapid expansion of its nuclear forces, without clear explanation, has introduced ambiguity. U.S. intelligence estimates project that China could have over 1,000 nuclear warheads by 2030, a dramatic increase intended to “close the gap” with the U.S. arsenal chinapower.csis.org. Yet Beijing has not acknowledged this buildup or clarified its purpose, nor announced any change to its doctrine chinapower.csis.org. The lack of transparency makes it hard for analysts to assess Beijing’s true red lines. Some wonder if China’s NFU pledge might be “squishy” – for instance, if a conflict threatened the Communist Party’s survival or if Chinese territory were under heavy conventional attack, would the leadership stick to NFU? There is also the matter of how China defines its territory: Beijing considers Taiwan to be a part of China; in a twisted interpretation, hawks could claim that a massive U.S. intervention on Chinese “sovereign soil” (Taiwan) justifies extraordinary measures. These concerns lead some U.S. planners to treat China’s NFU with caution, preparing as if Beijing might resort to nuclear use under dire circumstancesrand.orgrand.org.
China’s recent military activities provide mixed signals. On one hand, nuclear-capable systems have been more visible: for example, PLA Rocket Force exercises have prominently featured ballistic missiles (some potentially dual-capable), and Chinese nuclear-powered submarines are increasingly active in regional waters. On the other hand, China has not conducted any nuclear test explosions since the 1990s and has criticized other countries’ nuclear threats. Even during heated episodes like the 1995–96 Taiwan Strait Crisis and the 2022 drills, China did not move nuclear warheads into the open or overtly prepare nuclear strikes. This suggests a continued caution about introducing nuclear weapons into the Taiwan equation.
In summary, China’s stated nuclear policy and behavior thus far imply that an underwater nuclear explosion initiated by China is extremely unlikely barring all-out war. If Beijing adheres to its NFU policy, it would only consider a nuclear detonation if nuclear weapons were first used against it or possibly if the regime’s survival was truly at stake. Short of those triggers, detonating a nuclear device – whether underwater in the Taiwan Strait or elsewhere – would run counter to China’s strategic objectives, which favor restraining escalation to avoid a wider war with the U.S.
Taiwan’s Defense Posture and Alliance Considerations
Taiwan’s own actions and its alliances also influence escalation dynamics. Taiwan, for its part, has no nuclear weapons and remains under the protection of an informal U.S. “nuclear umbrella.” Taiwan did explore nuclear weapons secretly in the 1970s, but the United States pressured Taipei to abandon that program files.eric.ed.gov. Today, Taiwan relies on conventional defense and the promise of U.S. support. Over the past year, Taipei has embarked on significant defense reforms – boosting its defense budget, extending mandatory military service for young citizens, and focusing on asymmetric warfare preparations (e.g. mines, anti-ship missiles, and mobilization of reserves) warontherocks.com. These steps aim to raise the costs of invasion for China and buy time for U.S. and allied help to arrive in a crisis.
Taiwan’s security is bolstered by a web of partnerships. The United States is the key supporter, bound by the Taiwan Relations Act (1979) to provide defensive arms and maintain the capacity to resist coercion against Taiwan. U.S. forces regularly operate in the region; for instance, nuclear-powered attack submarines and aircraft carrier strike groups patrol the Western Pacific, signaling to China that Washington can bring formidable power to bearwarontherocks.com. Although the U.S. has not pledged automatic intervention, President Joe Biden has stated on multiple occasions that the U.S. would come to Taiwan’s defense if China launched an unprovoked attack, a stance that strengthens deterrence (even as official policy remains ambiguous).
Japan and Australia, two U.S. allies, are also critical. Japan in particular could be directly involved – it hosts U.S. military bases that would be pivotal in a Taiwan contingency, and Japanese leaders have called a Taiwan crisis a “security emergency” for Japan. This implies Japan might allow or even join U.S. military operations. Such allied involvement, however, might raise the risk of Chinese escalation: Beijing could see multiple powerful adversaries arrayed against it, potentially increasing desperation if things go poorly. Some Chinese officials have warned Japan and other allies not to intervene, even hinting at dire consequences if they do. For example, Chinese state media at times has mentioned nuclear retaliation in hypothetical scenarios where Japan intervenes, though these are usually dismissed as propaganda bluster. Still, the presence of U.S. alliances means a local war could quickly become a U.S.–China war, a fact that would weigh heavily on China’s calculus about nuclear use.
It’s worth noting that Taiwan’s own posture is one of endurance and defense, not counterattack. Taipei has no capability to threaten mainland China’s existence (aside from a minimal missile program). This likely reassures Beijing that it need not resort to extreme measures to deal with Taiwan itself. The real nuclear dimension comes in if U.S. forces are fighting China. In that scenario, U.S. doctrine and capabilities (including American nuclear forces on submarines and bombers in the Pacific) serve as a powerful deterrent against Chinese nuclear use. Beijing knows that any nuclear strike – even an underwater blast at sea aimed at U.S. Navy carrier groups – could trigger U.S. nuclear retaliation against Chinese targets. This deterrence logic from the Cold War still holds: neither side can use nuclear weapons without risking its own destruction.
Probability Estimate and Key Indicators
Bringing together these insights, we can assess the probability of an underwater nuclear explosion in 2025 amid China-Taiwan tensions as extremely low – effectively near zero unless a full-scale war erupts and spirals out of control. No credible public source has put a precise numeric probability on this specific scenario (due to the many uncertainties), but the general expert consensus is that nuclear use is highly unlikely. For example, the vast majority of surveyed experts (close to 90% in Taiwan, and a majority in the U.S.) believe China would not resort to nuclear weapons in a Taiwan conflict chinapower.csis.org. Analysts characterize the chance of nuclear escalation as a remote “tail risk”, one that cannot be completely dismissed but remains a last resort. The CFR’s designation of a cross-strait war as “moderate likelihood” in 2025 focustaiwan.tw should be understood as reflecting the risk of conventional conflict; the likelihood of that conflict involving nuclear blasts is far lower still.
That said, it is important to monitor key geopolitical indicators that could change this probability. A sudden deterioration in the strategic environment – for instance, a severe crisis triggered by a declaration of independence by Taiwan or an accidental clash that kills many – could raise the odds of war and, by extension, put nuclear options on the table in extremis. Signs that would increase concern include: Chinese leadership rhetoric explicitly invoking nuclear options (which so far has not occurred), deployment of nuclear warheads or explicit exercises near Taiwan, or movement of U.S. strategic assets (like nuclear bombers) into the immediate theater in a crisis (which could heighten Beijing’s fear of decapitation strikes). Fortunately, none of these indicators are present as of now. China’s nuclear forces remain largely in the background of the Taiwan situation; its nuclear ballistic-missile submarines patrol mostly in China’s coastal waters for second-strike deterrence, not in an aggressive posture.
In conclusion, while the China-Taiwan rivalry makes for a precarious flashpoint, the scenario of an “underwater nuclear explosion” in 2025 – implying actual use of a nuclear weapon under the sea, likely in the Taiwan Strait or nearby – is extraordinarily unlikely based on current assessments. Geopolitical and military tensions are indeed running high, but all sides have strong incentives to keep the conflict conventional. Nuclear weapons cast a dark shadow as a deterrent factor; they might be brandished in threats or alerts, yet remain sheathed. Barring a dramatic escalation or miscalculation, experts assess that the nuclear threshold will not be crossed in the Taiwan Strait. The probability of any nuclear detonation (underwater or otherwise) in this theater is effectively near-zero in peacetime, and would only marginally rise in a war – and even then only in a scenario of dire desperation. In essence, the risk exists but is extremely remote, and maintaining prudent diplomacy and military communication is key to ensuring it stays that way apln.networkapln.network.
Sources:
Council on Foreign Relations – Preventive Priorities Survey 2025 focustaiwan.tw
Taiwan Ministry of National Defense – reports on PLA exercises (via Focus Taiwan) armedservices.house.gov
War on the Rocks – China’s military and nuclear strategy for Taiwan conflict warontherocks.com
CSIS ChinaPower Survey 2023 – Expert views on China’s willingness to use nukes chinapower.csis.org
Atlantic Council – Analysis of nuclear weapons’ role in a Taiwan crisis atlanticcouncil.org
Asia-Pacific Leadership Network (APLN) – Nuclear Escalation in a Taiwan Strait Crisis? (Ayson, 2021) apln.network
RAND Corporation – Denial Without Disaster: Keeping U.S.–China War Below the Nuclear Threshold rand.org
News sources (Focus Taiwan, Foreign Affairs) on cross-strait conflict risk focustaiwan.tw
Historical context and expert commentary on nuclear escalation risks in East Asia tandfonline.com