Prevention, Again

By Xiaodon Liang

“What you’re asking is are we preparing plans for a preventive war, right? … A war that would prevent North Korea from threatening the United States with a nuclear weapon.”
– National Security Advisor H. R. McMaster, August 2017

The distinction between preemptive and preventive war, left fuzzy after the last major debate before the Iraq War, is relevant again. The public discourse, however, has featured ambiguities in vocabulary that threaten to muddle our understanding of military options and their lawfulness.

A critical ambiguity arises from differences in how the terms “preemption” and “prevention” have been used in the separate but overlapping nonproliferation and public international law literatures. Adding to the confusion, there are also general strategic meanings to the two words that security studies analysts and scholars have used for generations.

For the past 15 years, those following the evolution of the preemption/prevention distinction most closely were those lawyers tracking the global war on terror and its many associated conflicts. The Obama Administration in its final months took the stance that use of force in Syria against the Islamic State was justified not only in collective defense of Iraq, but also in preemptive defense of the United States itself against an imminent threat of armed attack. It offered an unweighted and expansive list of factors for determining the imminence of a threat from a non-state actor.

But confusion over how to define imminence sprang originally from the fear of weapons of mass destruction (WMDs). Remember that a key driver of the Bush administration’s 2002 doctrine of preemption (or prevention), outlined in that year’s National Security Strategy (NSS), was the fear of rogue states and their WMD capabilities.

Three Conceptions of Prevention and Preemption

The following table presents three different options for U.S. use of military force against North Korea and sums up how the different usages and interpretations of “prevention” and “preemption” relate to each other within and between (1) the nonproliferation academic community, (2) policy-makers and scholars of strategic studies, and (3) the international legal community. (For the purposes of this chart and article, only the imminence dimension of lawfulness is taken into consideration while proportionality is ignored, and questions of the law of armed conflict are left untouched entirely.)

Within the nonproliferation community, “prevention” has most often been used to describe action taken to stop a country from acquiring a credible nuclear weapons capability. An example would be Israel’s attack on Iraq’s Osirak reactor in June 1981, which set back Saddam Hussein’s nuclear program. This usage of “prevention” probably aligns most closely with a layman’s understanding of the term, and is likely what McMaster had in mind. For those nuclear scholars who believe that North Korea already has a good-enough intercontinental ballistic missile with a good-enough reentry vehicle and a good-enough nuclear warhead, the window for a “preventive” war has already closed and McMaster’s statement suggests a delusional state of denial in the National Security Council.

However, strategists and policy-makers have traditionally used a slightly different meaning of “prevention.” Preventive war is understood, as described by James Wirtz and James Russell in the 2003 debate on the Iraq War, as an attack initiated when a state decides that “war is inevitable, and that it is better to fight now while the costs are low rather than later when the costs are high.” Preemption, on the other hand, is “nothing more than a quick draw” – attacking first after receiving strategic warning of an enemy’s imminent offensive. Perhaps the most frequently cited example of such a quick draw was the Israeli preemptive attack in June 1967, following strategic warning of a forthcoming Arab assault. Thus, the nonproliferation understanding of “prevention” falls within the general strategic concept of prevention, but does not exhaust it. From a purely military perspective, as Colin Gray argued, there is nothing in military strategic theory that sets apart preventive war from any other type of conflict.

Legal scholars of jus ad bellum (i.e. the law of going to war), on the other hand, have a different understanding of . Critically, “preventive” war is not itself a term defined in law. Some lawyers eschew “prevention” altogether, differentiating only between legal and illegal types of “preemption” (or, “anticipatory self-defense”). Those that do make use of “prevention” use it to label those acts of preemption which would be clearly illegal given the imminence of a threat, in contrast with lawful “preemption.” (Further confusing matters, not all states in the international system would accept even “preemption” as lawful.)

Before the introduction of the 2002 Bush Doctrine, what constituted lawful preemptive self-defense was, by a broad consensus (notwithstanding some limited and inconsistent deviances by U.S. officials), understood to mean a threat of armed attack that is imminent –  that is, “instant, overwhelming, and leaving no choice of means, and no moment for deliberation,” according to the classic precedent set in the Caroline correspondence of 1841-1842. The 2002 NSS stated that in practice, this meant “most often a visible mobilization of armies, navies, and air forces preparing to attack.”

In the 2002–2003 debate and afterward, supporters of the Bush administration argued that this traditional test was no longer sufficient in an age of terrorism and rogue states, and that therefore the criteria for lawful preemption should be expanded to include prevention—in the strategists’ sense described above. Traditionalist critics responded that this expanded legal conception of preemption could no longer be called by that name and should be labeled what it was: prevention.

Implications and Responsibilities

The confusion over prevention and preemption, both in military and legal terms, casts a penumbra of uncertainty over the policy debate on North Korea’s nuclear program. For one example of how this uncertainty might be exploited, we face the prospect of officials and pundits arguing that the time for “prevention” (in the nonproliferation sense) has passed, and then, through a discursive sleight of hand, that therefore any action the United States might take would logically be the opposite of “prevention,” namely, “preemption.” Following this logic, the implication would be that the military action in question must be lawful and therefore legitimate.

For Americans and allies concerned about the legality of different military options, the failure of public figures and editorial rooms to distinguish clearly between preemption and prevention is a severe abdication of responsibility. It is unfair to expect defenders of the decaying liberal international order to master the vocabularies of three different policy debates before they can comprehend what it is they are speaking for or against.