North Korea has large incentives to use a tactical nuclear weapon—or several of them—early in another conflict on the Korean peninsula. Deciding how to respond to this is probably the most important contemporary debate inside the US-South Korea alliance.
A negotiated bargain that controls North Korean weapons of mass destruction would, of course, be the ideal way to avoid such a conflict, but any such deal seems highly unlikely. The most likely window for a breakthrough came during the overlapping ‘dovish’ presidencies of American President Donald Trump and South Korean President Moon Jae-In. But it has closed. For a brief moment, North Korean leader Kim Jong-Un faced the most negotiation-interested leaders in the history of his country’s primary geopolitical opponents – the US and South Korea. Trump particularly was a unique American president regarding North Korea – willing to meet Kim repeatedly without preconditions.
Tragically, Kim missed this Trump-Moon opportunity in 2018-2020. He offered only one deal to Trump, and it was so balance-negative for the allies that Trump had to reject it. So the North Korea debate in the democratic world—particularly in South Korea, the United States, and Japan—has reverted to traditional, hawkish approaches. If North Korea will not bargain—or, more specifically, if it will only propose lopsided deals—then the allies must consider military responses to the possibility of North Korean first-use.
There are three reasons that North Korea will likely use nuclear weapons first if war erupts on the Korean peninsula: Operationally, Pyongyang will face an intense “use-it-or-lose-it” dilemma regarding its weapons of mass destruction as soon as a war starts. Strategically, its conventional military is quite inferior to the forces ranged against it. And grand strategically, any serious conflict between the two Koreas will quickly become existential for the North.
I suggest two responses to this difficult challenge for the United States and its allies: At the time of attack, the allies should respond with nonnuclear retaliation as long as politically feasible, in order to prevent further nuclear escalation. However, this will be difficult given the likely post-strike panic and hysteria. So, in preparation, the US should deconcentrate its northeast Asian conventional footprint, to reduce North Korean opportunities to engage in nuclear blackmail regarding regional American clusters of military equipment and personnel, and to reduce potential US casualties and consequent massive retaliation pressures if North Korea does launch a nuclear attack.
North Korean first-use incentives. The incentives for North Korea to use nuclear weapons first in a major conflict are powerful:
Operationally, North Korea will likely have only a very short time window to use its weapons of mass destruction. The Americans will almost certainly try to immediately suppress Northern missiles. An imminent, massive US-South Korea disarming strike creates an extreme use-it-or-lose-it dilemma for Pyongyang. If Kim Jong-Un does not use his nuclear weapons at the start of hostilities, most will be destroyed a short time later by allied airpower, turning an inter-Korean conflict into a conventional war that the North will probably lose. Frighteningly, this may encourage Kim to also release his strategic nuclear weapons almost immediately after fighting begins.
Strategically, North Korea’s conventional military is almost certainly insufficient against capabilities. The (North) Korean People’s Army (KPA) is large but its equipment is technologically outdated. Sanctions limit the North’s production and fuel reserves. The country’s chronic malnutrition likely affects its soldiers’ health and fitness. Allied air supremacy would expose North Korean military assets to intense, immediate bombardment. Allied superiority in almost every area—logistics, communications, intelligence, surveillance, and weaponry—would be tremendous.
The North can leverage its proximity to South Korea’s center of gravity, the massive Seoul-Kyeonggi-Incheon corridor of northwestern South Korea. This area is uncomfortably close to the demilitarized zone, and North Korean forces are flush against the border to threaten it with massive missile and artillery bombardments. But this conventional countervalue threat—particularly the well-publicized artillery threat to Seoul—does not undermine South Korea’s military capabilities. The South Korean military would likely win a Korean-only conflict, and with American assistance, the North’s defeat would be crushing.
North Korea’s dysfunctional economic model, compounded by sanctions, make catch-up impossible. Its inability to close the conventional military gap is an obvious reason for the North’s construction of nuclear weapons, and Pyongyang has unsurprisingly talked up tactical nuclear weapons and their use. Without them, the North would lose the war, and strategically, using them sooner rather than later—before the KPA starts to lose on the battlefield—would be its best move.
On the grand strategy level, nuclear first-use is the Kim regime’s best chance at survival in a war. Defeat would bring regime change, and probably annihilation for the Kims. This is a critical difference between North Korea, on the one hand, and China and Russia. Russia has probably not used nuclear weapons in Ukraine because the war is not existential. A defeat there is not an offensive threat to the Russian state or territory, or to the regime of President Vladimir Putin. Similarly, if China were to be defeated around Taiwan, that would not lead to an invasion of the mainland or national collapse. Neither Ukraine nor Taiwan has revisionist intentions against their opponents. South Korea and its American ally do, so the consequences of defeat for North Korea are far worse than for Russia or China.
The South Korean constitution claims sovereignty over the entire Korean peninsula. A conventional second Korean War would open the possibility of national unity as the KPA was defeated on the battlefield and the South Korean army moved north. Nationalist hopes throughout the peninsula would soar. And for America, the opportunity to finally rid itself of one of its worst adversaries—to push for final victory on Southern terms— would be very tempting.
Because any serious Korean conflict would quickly become existential for the Kim regime, the incentive to launch nuclear weapons first—to deter or slow a march northward by the victorious allies—would be tremendous. China might militarily assist the North, per their alliance requirements, but that commitment is not very credible now. The Sino-North Korean relationship is transactional not affective. Instead, escalating to deescalate—using tactical nuclear weapons, with threats of further strikes unless the allies stop—would likely be the Kims’ best chance to prevent a catastrophic defeat.
In short, North Korea has massive first-use incentives. If it will not bargain to reduce its stockpile, then fashioning an agreed alliance response is critical. And the alliance should do it now. The first wartime use of a nuclear weapon since World War II will likely ignite global panic and terror. That would be a terrible, heated time to think through the allied response. There will be immediate calls for revenge in kind, if not massive retaliation. That would threaten a major US-North Korean nuclear exchange which could then chain-gang other regional players into the conflict too.
How should South Korea and the United States respond? For the United States and its allies, there are two reasonable responses—preparatory and contemporaneous—to the tough dilemma posed by North Korea’s nuclear weapons.
Before the North can attack, the allies should prepare by deconcentrating America’s northeast Asian force structure, for two reasons: North Korean will likely make immediate nuclear missile threats against regional concentrations of Americans to constrain US options in a Korean contingency. US military bases in South Korea and Japan—especially a very large site like Camp Humphreys, located just 40 miles from Seoul—present obvious missile targets for the North. They concentrate US citizens and assets; missile defense cannot assuredly defend them; and they can be taken hostage with missile strike threats.
Russia’s nuclear weapons have blocked direct NATO involvement in the Ukraine War. North Korea will likely try the same in Korea by threatening US east Asian bases. If North Korean nuclear blackmail can prevent, or at least slow, US assistance to South Korea, then Pyongyang’s chances of victory—coupled with tactical nuclear weapons use against the South Korean army—rise.
Were North Korea to strike American regional sites, the resultant mass US nuclear casualties would place nearly irresistible pressure on the US president to respond with nuclear weapons. Congress and the public would be outraged and demand retribution. America’s tendency to geopolitically overreact, to use extraordinary levels of force in conflicts, is well-established. The larger the US death toll, the greater would be the domestic call for massive retaliation. That could spark a regional nuclear chain-gang.
Traditionally, US soldiers in South Korea have been considered a “tripwire.” Their early deaths in a war would ensure an enraged American public and Congress, and therefore a commitment to fight on South Korea’s behalf. This was probably valuable alliance affirmation in the era of conventional inter-Korean competition. But in today’s nuclearized and missilized peninsular environment, that tripwire constrains US options and portends a spiraling regional confrontation after a likely American overresponse. Recently, the United States has been concentrating its South Korean basing for logistical reasons. Inadvertently, in this Korean missile age, the US is also offering attractive missile targets to the North.
Next, if the North does launch a nuclear attack, the United States should respond conventionally, not with nuclear weapons, as long as politically feasible. The political pressure to retaliate in kind, or with even greater nuclear force, will of course be tremendous, particularly if there were American casualties, which is likely given South Korea’s high population density. But there are many reasons why an immediate US nuclear response would be a mistake:
- The United States and South Korea would initially retain conventional superiority despite Northern tactical nuclear strikes. North Korean limited nuclear war options are not necessarily battlefield-decisive. Military necessity would probably not require nuclear retaliation, so as long as North Korean nuclear use remained limited to low-yield strikes.
- Operationally, nuclear blasts would irradiate the battlefield, making it harder for allied forces to advance northward and finish the conflict. Adding US-created blast zones to those created by the North would worsen the problem. The Korean peninsula is 70 percent mountainous and only 150-200 miles wide. So the relevant battlespace—mostly between the west coast and the peninsula’s mountain spine—is already narrow; more nuclear blast zones would constrain allied maneuver even further.
- US nuclear restraint would help swing global opinion—particularly in China and Russia— behind the allies. China and Russia oppose Korean unification. They will be tempted to intervene in a conflict to save their valuable spoiler with a long record of distracting their American competitor. Northern nuclear use could dramatically alter that calculus, encouraging Beijing and Moscow to remain neutral or even assist an allied victory out of sheer fear of North Korean behavior. US nuclear retaliation would override any such re-evaluation.
- Conversely, US nuclear use in Korea might chain-gang China and Russia into the war. As the Ukraine War demonstrates, a major conventional conflict involving a nuclear power can be geographically contained. A second Korean war need not spiral out of control. But US nuclear use near China and Russia would pressure both to intervene to save the North from elimination.
- US nuclear strikes would substantially worsen the reconstruction burden on a post-unification Korea run by Seoul. Blast zones from Northern nuclear strikes would be costly to rehabilitate; US nuclear strikes would only add to the load. That South Korea has revisionist intentions on North Korea—that it wishes to absorb it— substantial alters the cost-calculus of American nuclear use. The United States and South Korea would have to pay to decontaminate and rebuild after victory, which is not an element of US nuclear thinking regarding traditional opponents like China or Russia.
Unresolved issues. I have broached only a few of the many strategic problems created by North Korea’s unchecked nuclear and missile programs. The situation will worsen as North Korea builds a submarine-based deterrent, improves its targeting with satellites, develops multiple-warhead missiles, and so on. Conventional deterrence in Korea may be stable, but nuclear deterrence is probably not. A stable, enduring nuclear stalemate is unlikely in a dyad as asymmetric as North Korea and the US/South Korea.
Three policy questions flow from this analysis:
Should the allies launch a massive aerial disarming strike in a conflict? As discussed above, North Korea’s fear of that strike incentivizes its nearly immediate first-use. That, in turn, incentivizes exactly that immediate and large allied disarming strike. Each action responds to the other in worsening regressive spiral. When moving first has huge strategic advantages, the result is a hair-trigger balance encouraging preemption.
Should South Korea build nuclear weapons? North Korea likely hopes that its nuclear weapons—particularly their threat to the American homeland—will blunt US assistance to South Korea in a conflict, much as oblique Russian nuclear threats have retarded NATO assistance to Ukraine. Direct local nuclear deterrence might stay North Korea’s hand by reducing its nuclear weapons ‘wedge’ between nuclear-but-distant America and nonnuclear-but-proximate South Korea. US objections to South Korean nuclearization turn on the erosion of nonproliferation norms, but such fears are likely exaggerated.
Should the United States and South Korea give up on unification? Bolstered by massive inter-Korean economic and conventional asymmetries, Seoul’s desire to unify makes any serious Korean conflict an existential one for Pyongyang. An existential threat is an obviously compelling reason to build nuclear weapons. Surrendering South Korea’s pretension to unity might reduce North Korea’s perception that it must have nuclear weapons. South Korean progressives such as former President Moon Jae-In seem willing to countenance such a move to escape from the pressures sketched in this essay. The downsides are costly, though: North Korea might not keep its denuclearization word; North Korea’s population would be lost to history’s worst orwellian tyranny; and the US-South Korea alliance would likely fracture in obsolescence after an inter-Korea reconciliation.
There is no obvious policy answer to the North Korean first-use problem. All the responses suggested above have clear downsides. US regional deconcentration, for example, would be expensive and complicated, and South Korea and other US regional allies might read it as retrenchment or partial abandonment. Sanctions have blunted the North Korean problem for decades; without them, the problem would be even worse than it already is. But they are a stop-gap measure. The North Korean program marches on despite them, and China and Russia will not suddenly enforce them properly after two decades of ignoring pleas to do so.
We are approaching a critical mass of North Korean nuclear weapons and delivery systems which will demand a more radical solution—perhaps a hawkish one, such as South Korean nuclearization; perhaps a dovish one, such as South Korean recognition of North Korea. But the status quo—of allied half-measures, rickety sanctions, kicking the can down the road, hoping China will strong-arm North Korea, hoping missile defense will eventually work well enough to provide some ‘roof,’ and so on—is increasingly unsustainable.