On March 2, 2016, Kim Jong Un gave direction to the military to “get the nuclear warheads deployed for national defense always on standby so as to be fired at any moment.” The North reiterated versions of this formulation for days afterwards, including a “preemptive nuclear strike of justice.” These threats drew international attention because of concerns about the prospect of imminent violence, particularly in the wake of unprecedented UN sanctions and the kickoff of Key Resolve, the combined US-ROK annual military exercise.

But focusing on the possibility of near term violence obscures a potentially more dangerous longer term shift: Is North Korea signaling an intention to embrace tactical nuclear weapons? The answer is still unclear, but that option seems increasingly plausible. This should become a serious line of debate for Korea watchers because such a turn has critical consequences for how we think about deterrence and war-fighting on the Korean peninsula.

Why a Tactical Nuclear Turn Is Plausible

The threat of preemptive strikes from North Korea is hardly new. In 2010 alone, North Korea threatened a “preemptive nuclear attack” 20 times. And the typical formulation of North Korean threat rhetoric has often been to establish some “red line” condition—the imposition of sanctions in the 1990s, for instance—that would lead to North Korea launching a full attack, even at the risk of suicide. Scholars (including me) have likewise argued that North Korea has strong incentives to launch preemptive strikes if it believes the survival of the regime is in jeopardy.

While Kim’s recent nuclear threats are in keeping with the types of vitriol the North has unleashed in the past, they are also suggestive—in part because it has a continuous track record of these types of threats—of a North Korea that sees its nuclear weapons as inherently usable. Declaring the deployment or operationalization of nuclear weapons is as close as outside observers are likely to get to North Korea offering doctrinal specificity, and such statements imply Pyongyang may see its nuclear arsenal as something more than a symbolic shield against an invasion (notably, the North also links—rather than decouples—its references to nuclear attacks with the Korean People’s Army, which leaves open the interpretation they are an intrinsic part of warfighting).

But the plausibility of North Korea going down the path of developing tactical nuclear weapons derives from more than merely parsing its external messaging in a particular way, or the fact that Kim made the nuclear readiness statement during the unveiling of a new multiple rocket launcher system. A tactical turn for North Korea would also reflect the dictum that credible threats are usable threats. North Korea must know that it has a credibility problem thanks to a history of bluster. Nuclear-armed missiles do not help remedy that problem; their only plausible kinetic use would be to try to stave off imminent invasion or regime decapitation. North Korea has many goals beyond just survival though, and the military instrument has long been one way it pursues these goals. The question is whether the Kim regime believes that nuclear weapons can be used for something other than survival. The answer, unfortunately, may well be that North Korea believes employing nuclear-armed artillery, rockets, landmines or anything else that would result in low-yield nuclear detonations against localized targets in South Korea will not trigger massive alliance retaliation.

In the past, most crises on the Korean peninsula have been triggered by an alliance caught off guard by North Korean violence despite, in many cases, receiving advanced and explicit warnings from the North about what it intended to do. The reason for the alliance’s historical dismissal of these threats, of course, was entirely due to the latter’s track record of empty threat-making; it was impossible for American and South Korean officials to separate meaningful signals from oceans of noise. Tactical weapons do not make up for this history of hollow threat rhetoric, but they are generally thought of as more employable during combat scenarios than nuclear-armed ballistic missiles.

Our own history of developing tactical nuclear weapons for the European theater originated with the goal of usable—and by extension, more credible—options to counter a Soviet invasion of Europe without automatically being boxed into launching intercontinental ballistic missiles (and therefore unrestricted nuclear war). Minimally, the development and deployment of tactical nuclear weapons makes their use thinkable; militaries will plan to use them if they have them. So to the extent North Korea wishes to shore up its threat credibility problem or attempt to extract coercive leverage from its nuclear arsenal beyond just existential deterrence, tactical nuclear weapons may seem a logical (if mistaken) way of doing so.

The Danger of a Tactical Nuclear Turn

North Korea is on a trajectory with its nuclear and missile programs to achieve an assured second-strike nuclear capability. But if North Korea develops tactical nuclear weapons, it opens the door to operational first-use for reasons of both battlefield efficiency (i.e., the most damage for the least effort) and deterrence (i.e., the implied threat that things may get out of hand). The purpose of its missile forces—a kind of mutually assured destruction—would remain unchanged but there may be a doctrinal distinction between strategic and operational forces.

This path poses a distinct danger because, for the United States, it should not matter whether the nuclear threshold is breached with strategic or tactical weapons. Nuclear first-use—even if only with low-yield, non-strategic weapons—would force the United States into a nuclear warfighting posture, or more precisely, fighting limited conflicts even as an adversary employs nuclear devices. This increases the risk that the United States would resort to nuclear retaliation, which the last formal US Nuclear Posture Review (conducted in 2010) continues to permit as an option. And even if the United States avoids nuclear options itself by limiting alliance counter-attacks to conventional ones, it has no experience fighting nuclear-armed adversaries. We do not know how to “win”—or even what “winning” looks like—when waging military campaigns against nuclear-armed adversaries. What is more, North Korea’s early use of even one low-yield nuclear device may be sufficient to trigger a full-scale US or alliance invasion. Therefore, North Korean employment of tactical nuclear weapons would pose a greater risk of miscalculation and conflict escalation on the Korean peninsula.

Unless North Korea comes out and plainly describes its intentions with regard to operational nuclear employment, the task for Korea watchers is to think through what types of evidence would confirm or disprove suspicions that it is considering a tactical turn with its nuclear doctrine. Unfortunately, past scholarship has not offered much to work with; there is no reliable set of indicators for predicting tactical nuclear developments.

Nevertheless, North Korea’s rhetoric suggests the idea that nuclear weapons are usable. That may be a mere bluff given North Korea’s track record of cheap talk and its emphasis on a strategic deterrent (ballistic missiles), but that future possibility should be taken seriously by the United States and South Korea. Specifically, the possibility of a tactical turn requires preparing for limited military campaigns despite the specter of nuclear threats, waging such campaigns should North Korean adventurism require it, and thinking through how the alliance might react to tactical nuclear scenarios. The most dangerous periods on the Korean peninsula have historically been those brought on by surprise. We should avoid such a fate again by preparing for what may appear unthinkable but remains entirely plausible.