The Consequences of an Invasion of South Korea

Key Takeaways

• A second Korean War could be far deadlier than the first, with modern nuclear and conventional capabilities raising the potential human cost.

• Pyongyang has expanded nuclear, missile, conventional, cyber, biological, and chemical capabilities, maintaining a deterrent posture while preparing for potential conflict.

• Seoul relies on advanced conventional forces, a growing blue-water navy, air superiority, and a US nuclear umbrella to counterbalance North Korean aggression.

• Any conflict would likely draw in the US, China, and potentially Russia, with the scale and impact magnified by modern military and nuclear capabilities.

• An invasion would likely start with missile and artillery barrages, cyberattacks, and limited ground operations, followed by South Korean counteroffensives supported by the US.

• Even a localised conflict would disrupt global supply chains, financial markets, shipping, and cybersecurity, forcing firms to adapt at short notice.

History Repeating

Living with the awareness that war could break out at any given time has been a perennial aspect of life for those living on the Korean peninsula. While Koreans have particularly compelling reasons to fear such a prospect, a second iteration of the Korean War would have consequences reaching far beyond East Asia. The catastrophic nature of the Korean War, fought between 1950 and 1953, provides a stark reminder of the implications of such a conflict. Estimates place the death toll between three million and five million, more than half of which were civilians. Although the conflict concluded with an Armistice Agreement, with no formal peace treaty signed, the war has essentially been paused rather than resolved.

There is convincing evidence to suggest that a second iteration of the Korean War would be even more devastating than the first. Both sides possess far more lethal weapons than before and the one or both of China and the United States (US) could intervene. Other countries such as Russia, Japan and various NATO allies are also likely to become involved in one form or another. While the severe implications of a second Korean War have acted as a powerful deterrent, Pyongyang has made its intentions clear. Among many of his inflammatory remarks aimed at the US and South Korea, North Korean Leader Kim Jong Un has threatened to “deal a deadly blow to thoroughly annihilate them by mobilising all the toughest means and potentialities without a moment's hesitation”. Analysts debate whether his comments should be taken seriously or labelled as posturing designed to achieve the strategic objective of reinforcing deterrence.

The Threat Posed by North Korea

With fears of a second Korean War shared on either side of the Military Demarcation Line (MDL), Pyongyang and Seoul have both rapidly expanded and advanced their military capabilities in the decades following the armistice. When it comes to the North Korean military, the country’s nuclear weapons programme immediately comes to mind. As outlined by the Congressional Research Service’s 2025 report: “Over the past decade, North Korea has advanced its nuclear weapons and ballistic missile programmes, raising the threat Pyongyang poses to the US homeland, US allies in East Asia, and US interests”. Despite the international community imposing sanctions and trade restrictions, no meaningful progress has been made towards North Korea’s denuclearisation.

With the window for military action to address the nuclear threat having closed decades ago, the threat posed by North Korea’s nuclear programme is unlikely to subside. As outlined by the US Intelligence Community’s 2025 report: “Kim has no intention of negotiating away his strategic weapons programmes, which he perceives as a guarantor of regime security and national pride”. Evidence suggests that the country’s nuclear arsenal is expanding, while its ballistic missile technology grows increasingly sophisticated. While the country has never disclosed the number of nuclear warheads in its possession, the figure is thought to be around 50. These are deliverable through a range of ballistic missiles, including short and medium-range missiles that could target South Korea and Japan, intermediate-range missiles capable of reaching US bases in the Asia-Pacific, and intercontinental ballistic missiles (ICBMs) designed to threaten the US mainland. Additionally, the passing of a law in September 2022 lowered the threshold for Pyongyang to use nuclear weapons in certain scenarios, including a declaration of intent to initiate pre-emptive nuclear attacks.

While Pyongyang’s nuclear weapons programme often attracts media headlines, the threat posed by North Korea also extends to its conventional military capabilities. The country boasts one of the world’s most formidable standing armies, with roughly 1.3 million active military personnel (the fourth largest in the world). Despite North Korean units sustaining significant casualties in Russia’s Kursk region against Ukrainian forces, the losses constitute a small fraction of total manpower. Pyongyang also possesses a massive rocket arsenal, with an estimated 8,500 field artillery pieces, 5,100 multiple-launch rocket systems, 100 170-millimetre self-propelled guns, and 200 240-millimetre multiple-launch rocket systems. Many of these are strategically positioned near the border, close to the South Korean capital, Seoul. North Korea is also believed to have roughly 4,300 tanks in its arsenal.

Due to a historical focus on prioritising land-based military strength, North Korea’s brown-water navy is unimpressive. The fleet consists of 60 diesel coastal and mini submarines, the majority of which date back to the 1960s and 1970s, as well as small patrol vessels and corvettes. Naval operations are therefore focused along the coastline, rather than projecting power far beyond the shore. However, it is important to acknowledge that there has been an uptick in efforts to expand these capabilities by building new warships, such as the new Choe Hyon-class, and developing nuclear-capable submarines, including the Hero Kim Kun Ok. While a stronger North Korean navy would have potentially broad implications for regional security and global geopolitical dynamics, the country’s limited naval technological and industrial capacity, coupled with sanctions that restrict access to critical technologies and materials, is likely to slow progress.

The Korean People’s Air and Anti-Air Force (KPAAF) is similarly unremarkable, with an overreliance on Soviet-era jets. According to The Cove: “The KPAAF is largely composed of ageing aircraft with roughly 800 combat aircraft, including MiG-21s, MiG-23s, and MiG-29s, 300 helicopters, including Mil Mi-2 and Mi-8/17 variants and a range of air defence systems including SA-2, SA-3, SA-5 surface-to-air missile systems and newer indigenous systems”. Again, North Korea is seeking to change this situation. In 2023, North Korea unveiled AI-equipped unmanned aerial vehicles (UAVs) resembling American RQ-4 Global Hawk and MQ-9 Reaper unmanned attack aircraft, named the Saebyeol-4 and Saebyeol-9. In March 2025, Kim also unveiled the country’s first airborne early-warning aircraft.

Attention should also be given to North Korea’s biological and chemical weapons. biological weapons use living organisms, such as bacteria and viruses, to deliberately cause mass sickness, death, or disruption. Whereas chemical weapons use munitions, devices, and other equipment to cause death or harm by dispersing toxic substances. According to one disconcerting report published by the Centre for Strategic and International Studies, the country’s biological weapons pose a serious potential threat to the US and its strategic partners”, to an extent that “could be even more lethal than nuclear weapons,” which are also less cost-effective. Although the country’s chemical weapons programme is extremely secretive, CIA assessments believe Pyongyang has had one for many years, with a large stockpile of lethal agents. South Korea’s defence ministry has estimated a total reserve of 2,500 to 5,000 tonnes of various agents, including nerve agents like VX and sarin gas, blister agents such as mustard gas, and choking agents like chlorine, among others. The 2017 assassination of Kim Jong-un’s half-brother at Kuala Lumpur International Airport with the chemical nerve agent VX drew worldwide attention to North Korea’s chemical weapons capabilities.

While North Korea’s military capabilities have concerned world leaders for decades, unless a conflict breaks out, they serve little purpose other than deterrence. To apply pressure on adversaries without triggering a war, Pyongyang has expanded its use of hybrid warfare. One particularly key aspect of this has been the use of cyberattacks. The country’s cyberwarfare agency, Bureau 121, is responsible for coordinating cyberattacks, gathering intelligence, and generating revenue by hacking foreign entities. The unit, which is made up of around 6,000 hackers, was blamed by the FBI for a 2014 cyberattack that crippled Sony’s network. Reports have also emerged regarding the infiltration of Western firms by North Korean remote workers posing as legitimate contractors to generate revenue for the regime. It is anticipated that North Korean hybrid warfare will become more sophisticated and problematic in the coming years.

The Threat Posed by South Korea

Despite possessing the technical capacity to produce them, Seoul has opted not to develop nuclear weapons, instead relying on Washington to provide a nuclear umbrella. Under the terms of the 1953 Mutual Defence Treaty, both nations are obligated to treat an armed attack on either as a threat to their own security and respond appropriately. Although this does not explicitly require automatic military action, it has been interpreted as a commitment to defend South Korea with military means if attacked. South Korea’s military has shrunk to 450,000 active personnel due to a historically low birth rate, making an expansion in manpower necessary. The importance of this is made even more pressing given research suggesting that at least half a million would be needed to defend against an invasion from the North. Nevertheless, South Korean holds an advantage regarding the technological sophistication of its armed forces. In addition to boasting the second-largest artillery force in the world, albeit after North Korea, with 12,100 artillery pieces, Seoul has a wide range of sophisticated weapons systems. This includes around 1,100 K9 Thunder 155-mm self-propelled howitzers, considered to be the best in their class. South Korea also operates a significant number of rocket systems, including hundreds of K239 Chunmoo Multiple Launch Rocket Systems, various Hyunmoo ballistic missiles, and advanced air defence missiles, including the M-SAM and L-SAM.

The South Korean navy, which is transitioning from a green water to a blue water navy, is in another league compared with North Korea’s. The fleet consists of 147 vessels, including 13 destroyers, 17 frigates, 3 corvettes, and 21 submarines. Seoul is currently working on developing its first light aircraft carrier, the CVX-class, which will mark a major leap in its power projection capabilities. With over 800 aircraft, the ROK Air Force is formidable, blending Western technology with Korean innovation. The forces are spearheaded by F-35s, upgraded KF-16s, and F-15K Slam Eagles, which are supported by a robust multi-layered air defence system. South Korea is also in the process of upgrading its Airborne Early Warning & Control capabilities, having awarded a $2.26 billion contract to L3Harris to provide new Phoenix AEW&C aircraft. As a signatory to the Chemical Weapons Convention and the Biological Weapons Convention, South Korea is not known to possess chemical or biological weapons.

The Escalatory Impact of International Intervention

With the strategic, historical, and symbolic significance of the Korean peninsula raising the stakes of a conflict for countries around the world, a range of other countries would likely weigh in. The international intervention witnessed during the Korean War serves as an example of the inflammatory impact such interference can have. As the first major proxy conflict of the broader Cold War, the confrontation saw China and the Soviet Union intervene on behalf of North Korea, while the US-led United Nations coalition stepped in to support South Korea. Washington played a decisive role in repelling the initial North Korean invasion before leading the push beyond the 38th parallel into North Korea. Motivated by national security concerns, Chinese forces escalated the situation by subsequently intervening and reversing the gains made by UN forces. Although the Soviet Union refrained from openly entering the war with substantial ground troop deployments, it was involved from the outset as an essential supplier. By the end of the conflict in 1953, the US and China had sent 3 million troops collectively, with Washington also deploying one-fifth of its air force and nearly half of its navy. While Soviet personnel only numbered between two and three thousand, Moscow provided massive amounts of aid, including T-34 tanks, MiG-15 fighter jets, small arms, and essential supplies. Together, these international actors transformed a civil conflict into a major Cold War confrontation that has locked the peninsula into prolonged division.

Figure 1 – Photo of a soldier standing next to the 38^th Parallel in 1950

Although no two conflicts are identical, convincing evidence suggests that the US, China, and Russia would reprise their interventionist roles in a second Korean War. However, with military capabilities advancing significantly in recent decades, the potential consequences have increased exponentially. As such, the precise nature of their involvement would be different the second time around. During the Korean War, China was a backward, agrarian society devastated by decades of civil war. Beijing’s navy was a brown-water fleet consisting of small, unsophisticated vessels focused on coastal defence. The air force was embryonic, inexperienced, and largely equipped with older propeller planes. Although numerically large, the People’s Liberation Army was technologically primitive, lacking in heavy artillery and tanks. Comparatively, in 2026, China is a military powerhouse with an industrialised, market-oriented, export-driven economy. The country has thrived in its role as ‘the world’s factory’, propelled by rapid urbanisation, a booming population, and the expansion of private enterprise. As the world’s second-largest economy and a global leader in technology, the modernisation of the armed forces has become central to Xi Jinping’s ambition of overseeing China's emergence as the world’s leading superpower.

While China’s rise has been unprecedented, much has also changed for the US. Back in the 1950s, the US economy was heavily industrial and the Americans were building their first permanent overseas bases in Europe and East Asia. While nuclear weapons were emerging, delivery systems were rudimentary and conventional forces dominated strategy. Since then, the economy has shifted decisively towards services and technology, with industrial production largely offshored. Military capabilities have advanced across the board, transitioning from large-scale troop manoeuvres and mass unfocused artillery to unmanned systems and precision-guided munitions that achieve results from a distance. Today, the US has by far the most expansive military presence worldwide, with roughly 750 military outposts that facilitate global power projection.

Both countries now possess substantial nuclear arsenals. Beijing is believed to have 600 warheads and the world’s fastest-growing reserve. Comparatively, Washington has around 5,200 warheads hosted domestically and overseas in Turkey, Italy, Belgium, Germany, and the Netherlands. The pair also boast nuclear triad capabilities, blending land, sea, and air delivery systems. The size of the American and Chinese armies has shrunk since 1950, when the Korean War erupted. While currently in possession of the world’s largest army, China has witnessed a decline from 4.6 million to 2 million personnel. Meanwhile, the US army, which had 1.4 million personnel in 1950, currently stands at 1.3 million. The number has spiked at certain times due to wars, such as those in Korea and Vietnam. It would be incorrect to assume that the threat posed by either has diminished in a similar fashion to the number of personnel. Although technological advancements haven’t rendered large armies obsolete, they have made mass mobilisation much less important.

China boasts the world's largest land-based missile arsenal, as well as various munitions for targeting land and sea targets at a range of distances. Examples include the DF-41 ICBM, as well as short and medium-range missiles, such as the DF-2, DF-17, and DF-21. Beijing’s anti-ship ballistic missiles, primarily the DF-21D and DF-26, have gained a reputation as “carrier killers” due to their ability to target aircraft carriers with manoeuvrable warheads. The US possesses equivalent precision-guided systems, such as HIMARS, MLRS, GMLRS, and ATACMS, for striking targets at various distances. This is complemented by numerous howitzer systems, including the M109A7 Paladin, for mobility. Interestingly, in December 2025, the US Army confirmed that the M270A2 rocket artillery system was involved in live-fire testing in South Korea for the first time, reflecting Seoul’s priority status as a recipient of top-of-the-range US equipment. Regarding tanks, China, with 6,800, edges the US, with 4,600. However, Washington benefits from greater combat experience and fields a greater proportion of its tanks as modern, high-tech variants, such as the M1 Abrams.

In terms of naval power, with China's shipyards producing warships at an extraordinary rate, the People’s Liberation Army Navy now has the world’s largest fleet. This includes three aircraft carriers, 60 destroyers, 50 frigates, 70 corvettes, and 60 submarines. Whereas Washington has 11 aircraft carriers, 75 destroyers, 25 corvettes, and 70 submarines. China’s air force is thought to have roughly 2,150 combat aircraft, compared with the US, which has around 2,650. Chinese fighters, including the J-20 and the J-35, take centre stage. However, the American F-35, which is the backbone of the American fleet, is often cited as the most advanced, while the F-22 Raptor is thought to be the gold standard for pure air-to-air combat.

One key difference between the 1950s and present-day is Russia’s standing in the equation. During the Korean War, the Soviet Union was Washington’s undisputed arch-rival. However, today, many analysts put Russia in a distant third compared with the US and China in a range of metrics, including military strength and economic capacity. Additionally, with Moscow’s attention firmly fixed on Ukraine, if war were to again break out on the Korean peninsula, the Kremlin would likely play a less influential role compared with China. While an end to the Ukraine war does not appear imminent, it has to end at some point, and when it does, Moscow’s preparedness to intervene on the international stage will increase.

The Kremlin’s indebtedness to North Korea could also cultivate a sense of obligation to reciprocate Pyongyang’s support in Kursk. In September 2022, reports emerged that North Korea was sending armaments, including artillery shells and ballistic missiles, to support Moscow’s war in Ukraine. In Autumn 2024, this was expanded by Pyongyang, which sanctioned the deployment of troops in Kursk after Ukraine caught Russia with its pants down with a lightning offensive into the region. To date, Pyongyang has sent between 14,000 and 15,000 soldiers to support the Russian war effort.

While the Russian military is occupied in Ukraine, for Moscow to adopt a greater role in a second Korean war would still cause major problems for officials in Seoul and Washington. Russia has the largest stockpile of nuclear warheads in the world, estimated at around 4,300. Moscow is currently in the latter stages of a multi-decade modernisation programme to replace its Soviet-era nuclear-capable systems with newer versions. The country also fields Multiple launch rocket systems (MLRS), including the BM-21 Grad, BM-27 Uragan, BM-30 Smerch, and the 9A52-4 Tornado, which facilitate rapid, precise fire over long distances. This is complemented by self-propelled artillery systems, such as the 2S19 Msta-S and the 2S1 Gvozdika, as well as towed artillery guns, including the 2A65 Msta-B and the Pat-B howitzer. While Russian tank reserves have sustained heavy losses in Ukraine, they are still far from exhausted. Estimates believe the pre-war stockpile of 7,300 tanks has diminished to around 3,000. Russian defence factories are operating around the clock to replace those being destroyed.

The air force possesses a diverse fleet which, in typically Russian style, excels in sheer volume, with around 4,200 combat aircraft. Russia’s main bombers are still the Tupolev 160 and Tupolev 95, which were introduced in 1956 and 1972, respectively. The Sukhoi-35 is the country’s most advanced and primary operational fighter, which, though less advanced than the F-35, serves as the centrepiece of the air force. Regarding naval power, Russia has limited power projection capabilities. Its only aircraft carrier, the Admiral Kuznetsov, isn’t operational due to numerous technical issues. The ship is currently undergoing extensive repairs in Murmansk and the return date remains unknown. 83 corvettes make up the bulk of the surface fleet, alongside 10 active destroyers. However, these, along with much of Russia’s fleet, are ageing. Consequently, Moscow's naval threat is primarily derived from its submarine force, with eight Borei-class nuclear subs, also known as “boomers”, and five Yasen-class attack subs, leading the line.

Complicating Factors

Nothing is certain in international affairs. A range of countries have a clear interest in shaping the outcome of a second Korean War, and many possess the means to influence it through direct military intervention, material support, diplomacy, or other forms of engagement. With the interested parties possessing enough cumulative firepower to inflict irreparable damage to one another, the prospect of mutually assured destruction has prevented a second Korean war from breaking out. As mentioned, Washington, which has 28,500 troops stationed in South Korea, is treaty-bound to intervene in the event of an invasion. It remains unclear whether American and North Korean troops can face each other on the battlefield without the situation deteriorating into a nuclear exchange.

Kim may want to reunify Korea, but, assuming that he makes decisions based on his strategic interests, would he be prepared to launch an invasion, given the severe escalatory risks and the inevitable threat it would pose to his regime? While a North Korean decision to invade seems illogical from the outside, many analysts held similar views regarding a Russian invasion of Ukraine. To attempt an invasion, Kim would likely require an overwhelming sense that either success was assured or that an attack on North Korea was imminent. With the country’s system being built on projecting an image of strength and persecuting those who fail to tow the party line, the flow of information reaching Kim is heavily filtered and shaped by political incentives. Consequently, the logic behind his decision-making can be called into question.

It is worth addressing some of the holes that have developed in the American security umbrella. Doubts surrounding US security guarantees have intensified in recent years as Trump’s ‘America First’ agenda has undermined alliances previously thought to be iron-clad. Under President Biden, security cooperation with partners such as South Korea was considered a strategically useful means of checking China. But as one 2025 commentary from Chatham House highlights: “Unlike Biden, Trump views alliances as dependencies to be exploited by extracting maximum benefits to suit his America First agenda”. Trump has regularly complained about Seoul’s financial contributions towards hosting US troops and even threatened to withdraw or redeploy them. During a press conference in July 2025, he told reporters: “South Korea is making a lot of money, and they're very good. They're very good, but, you know, they should be paying for their own military”. If Trump were to pull the plug and instead refocus on the United States’ sphere of influence in the Western hemisphere, it would make the prospect of invading South Korea a far less daunting prospect for Kim. Admittedly, it is difficult to distinguish between which of Trump’s threats are credible and which are merely posturing aimed at extracting favourable concessions. In May 2025, the Pentagon rejected a Wall Street Journal report that claimed the US was considering withdrawing roughly 4,500 troops from South Korea. Nevertheless, according to a report published by the Centre for Strategic and International Studies: “Although a decision on troop withdrawals has not been made, the issue is under serious consideration at the Pentagon, US Forces Korea, and Indo-Pacific Command”.

Just as policymakers in Washington weigh the pros and cons of stationing troops in South Korea, similar debates would take place in Beijing regarding China’s potential role should another conflict break out. A reunified Korea in any form is unlikely to align with China’s strategic interests. Many analysts also hold that Chinese policymakers would take a dim view of another conflict breaking out so close to the mainland. While China and North Korea have a strategic partnership centred on convenience and the former viewing the latter as a useful buffer state, it is also known that Beijing considers Pyongyang to be unpredictable. This has been demonstrated on occasions in which China has joined the UN Security Council in condemning North Korea’s nuclear tests. For Beijing to intervene on behalf of the aggressor that initiated the war would be extremely risky. It’s one thing to slide a few ammo crates across the border, but to deploy Chinese troops and actively engage would be a different kettle of fish. In addition to being extremely bad PR with significant economic repercussions, it could also draw the country into a war with the US. What could tip the scale for China is if South Korea and the US successfully repelled a North Korean attack and subsequently encroach north toward the Chinese border, as occurred during the 1950s. In such a scenario, China’s strategic and national security concerns are likely to provoke a more robust response.

The Invasion – Why a North Korean Victory Will be Difficult

Once North Korea commits to an invasion, opportunities for de-escalation will rapidly diminish. Given that a nuclear conflict offers no viable path to victory, the immediate use of such weapons would represent an extreme and high-risk course of action. It is therefore more likely that Pyongyang would initially rely on conventional military force, reserving nuclear escalation as a last resort should regime survival come under direct threat. This dynamic creates a strategic dilemma for US and South Korean decision-makers. The more damage inflicted on North Korea during the early stages of a conflict, the greater the likelihood that Kim Jong Un would consider the use of nuclear weapons. Leaders in Washington and Seoul would therefore face a critical choice: pursue rapid and decisive operations aimed at eliminating North Korea’s nuclear capabilities and leadership before retaliation becomes possible, or limit objectives to repelling the invasion and restoring the pre-war status quo to reduce escalation risks.

A renewed conflict on the Korean Peninsula could unfold in several ways, shaped by decisions taken under intense time pressure and uncertainty. US and South Korean forces regularly conduct joint exercises to simulate a range of scenarios and while no conflict would follow a fixed script, analysts broadly anticipate a series of phases. The first of these would be a build-up phase. Advances in satellite imagery and surveillance technologies significantly reduce the likelihood of large-scale military preparations going undetected. This was demonstrated by the visibility of Russian troop movements prior to the invasion of Ukraine. However, North Korea differs in that it already maintains substantial forces, including artillery, rocket launchers, and mortars, positioned close to the Demilitarised Zone (DMZ). As a result, Pyongyang retains the ability to initiate hostilities with minimal observable preparation.

Figure 2 – Image Showing the Demilitarised Zone (DMZ) between North Korea and South Korea

A large and conspicuous forward deployment would be unnecessary and potentially counterproductive. While a repeat of the strategic surprise seen in 1950 is unlikely, preserving ambiguity and delaying clear indicators of intent would remain central to North Korea’s approach. Failure to do so risks prompting pre-emptive strikes, immediate retaliation, or more robust defensive postures from South Korea and the US. To this end, Pyongyang could employ deception tactics such as camouflage, false documentation, and false-flag activities. The effectiveness of intelligence collection and analysis during this phase would be decisive in shaping how the conflict progresses.

The opening phase of combat would likely involve an extensive artillery and missile barrage targeting key military and civilian infrastructure. Likely targets include government facilities, command-and-control centres, airbases, communications nodes, and energy infrastructure. Seoul, located approximately 50 km from the border, lies well within range and would be particularly vulnerable. As South Korea’s political and administrative centre, it would hold significant strategic and symbolic value.

South Korea would rely on layered missile defence systems, including Patriot PAC-3, Terminal High Altitude Area Defence (THAAD), the Korean Air and Missile Defence (KAMD) system, and counter-rocket, artillery, and mortar (C-RAM) capabilities. While these systems provide coverage across multiple altitudes and ranges, their effectiveness against massed artillery and rocket fire remains uncertain. Even with strong protection against strategic missile threats, saturation attacks could overwhelm defences.

The opening strikes would also extend beyond the physical domain. Cyber operations aimed at disruption and confusion would likely target power grids, financial networks, and military command-and-control systems, seeking to delay or degrade South Korea’s ability to coordinate a response. With hostilities underway, North Korea would have little incentive to conceal force movements. Mobile artillery units, multiple rocket launchers, and self-propelled guns would be redeployed rapidly to avoid counterstrikes once firing positions are revealed.

Figure 3 – Photo showing a North Korean KN-25 multiple rocket launcher

Within hours of the initial attacks, Kim Jong Un would likely issue a formal declaration of war. This would almost certainly frame North Korea’s actions as defensive, attributing responsibility to South Korea and the US. Such a statement would also serve to deter external intervention, with explicit or implicit nuclear threats directed at third parties. International reactions would follow quickly. Western governments would condemn the attack, while China and Russia would be more likely to call for restraint and dialogue, avoiding explicit alignment with either side.

Following the initial strike phase, Pyongyang would face several options, depending on the success of its opening operations. One option would be escalation through a second, potentially larger wave of attacks, possibly including ground incursions across the DMZ. Such an advance would be highly challenging given extensive fortifications, minefields, surveillance systems, and the likelihood of airstrikes. However, North Korea has constructed an extensive network of tunnels beneath the DMZ. While four have been discovered, South Korean intelligence estimates that up to 20 additional tunnels may exist.

Alternatively, Pyongyang could sustain pressure through follow-on attacks of reduced intensity, acknowledging the difficulty of maintaining the tempo and scale of the initial barrage over a prolonged conflict. A third option would be to consolidate and fortify existing positions in anticipation of a South Korean counteroffensive. Given the limited territorial gains likely from an opening bombardment, this approach would risk ceding the initiative to Seoul.

Regardless of Pyongyang’s next move, South Korea would move rapidly into a counteroffensive phase. Given the existential stakes, Seoul has invested heavily in preparing for such a scenario. Establishing air superiority would be a central objective. Surviving airfields would be used intensively to generate sorties, and while the airspace would initially be highly contested, analysts broadly expect South Korea, supported by the US, to gain control relatively quickly. North Korea’s ageing air force would struggle to compete against modern South Korean and US aircraft.

South Korea would expect the US to honour its obligations under the 1953 Mutual Defence Treaty. Although concerns persist about US isolationist tendencies and reduced confidence among South Koreans regarding Washington’s reliability, most analysts agree that US intervention remains highly likely. South Korea’s strategic importance, economic ties, and role as a key regional military hub make disengagement improbable. While US leaders have shown reluctance to commit large ground forces in recent conflicts, they have demonstrated a willingness to employ airpower and maritime pressure to achieve strategic objectives. This approach aligns with the 2026 National Defence Strategy, which emphasises “critical but more limited” support rather than large-scale reinforcement. US involvement could include the deployment of aircraft from bases in South Korea, Japan, and across the Indo-Pacific, as well as long-range strikes by stealth bombers against nuclear facilities and leadership targets. Naval assets, including carrier strike groups and submarines, would also likely be repositioned. These actions would align with OPLAN 5022, which includes options for leadership decapitation aimed at ending the conflict swiftly while avoiding prolonged war.

Even in the absence of direct US ground involvement, South Korea retains formidable independent capabilities through its Three Axis System. This framework includes pre-emptive strikes on nuclear and missile facilities (“Kill Chain”), layered missile defence (KAMD), and the Korea Massive Punishment and Retaliation (KMPR) plan, which focuses on eliminating North Korean leadership through precision strikes and special operations.

Several outcomes could follow the counteroffensive phase. A military stalemate could emerge, prompting de-escalation under international pressure and potentially leading to armistice negotiations and a return to the status quo. Alternatively, a highly successful South Korean campaign that threatens regime survival could provoke further escalation, including nuclear use, echoing the trajectory of the first Korean War but under far more dangerous conditions. A third scenario lies between these extremes. South Korea could achieve tactical success without pushing toward regime collapse, while North Korea, lacking sufficient external support, becomes unable to advance. The 1991 Gulf War offers an example of a conflict with a similar conclusion.

Business Implications

A conflict on the Korean Peninsula would trigger an immediate global economic shock. South Korea is a central hub for semiconductors, advanced manufacturing, shipbuilding, and electronics, meaning even limited disruption would ripple through global supply chains and affect production, pricing, and delivery timelines worldwide. Financial markets would react sharply. The South Korean won and regional equities would likely sell off, while global markets price in heightened geopolitical risk. Shipping routes in Northeast Asia could be disrupted, driving up freight costs and insurance premiums and adding to inflationary pressures. Cyber risk would also rise markedly. North Korea has a track record of targeting foreign companies and financial institutions, increasing the likelihood of cyberattacks on firms with exposure to South Korea, Japan, the US, and allied states. For businesses, the conflict would accelerate the shift from efficiency to resilience. Supply chain diversification, political risk management, and contingency planning would move from strategic considerations to operational imperatives.