Before the closing ceremonies of the Winter Olympics on Sunday, South Korea’s president announced that North Korea is interested in a diplomatic dialogue with the United States.
The welcome news comes after a year of extraordinary tensions between Washington and Pyongyang. Since Donald Trump took office in January 2017, North Korea has engaged in a record number of provocative actions, including test launching intercontinental ballistic missiles capable of striking the United States and test detonating a hydrogen bomb. In response, President Trump has threatened to “totally destroy” North Korea in the event of war. Moreover, the president declared earlier this month that his “nuclear button” is “much bigger & more powerful” than Kim Jong Un’s “nuclear button.” No previous American president has ever publicly threatened to use nuclear weapons in such a brazen and flippant way.
The nuclear standoff between North Korea and the United States raises a fundamental question of international law: Do the laws of war permit the use of nuclear weapons?
In most cases the answer is no. Any detonation of nuclear weapons in the vicinity of urban centers would violate two cornerstone laws of war: the prohibition on indiscriminate warfare and the prohibition on the targeting of non-combatants. But the question becomes much murkier when the proposed use of the weapon is in an area far removed from civilian populations, such as a tactical nuclear strike on a remote missile facility in the mountains. In such a scenario, the laws of war are remarkably unclear.
Basic Law of War Principles
Although international law expressly bans chemical and biological weapons, there is no international treaty that bans nuclear weapons. In fact, in a 1996 advisory opinion, the International Court of Justice expressly rejected the notion that customary law prohibits the use of nuclear weapons. In an 11-3 ruling, the court held that “[t]here is in neither customary nor conventional international law any comprehensive and universal prohibition of the threat or use of nuclear weapons as such.”
The upshot of the ICJ’s ruling is that the use of nuclear weapons is governed by traditional law of war principles just like any other weapons system. In other words, strange though it may seem, under international law a 5-megaton nuclear warhead is analyzed under the same principles as a 50-pound conventional bomb.
Nevertheless, despite the lack of an international treaty that expressly regulates the use of nuclear weapons, there are three general prohibitions in the laws of war that effectively render most—but not necessarily all—uses of nuclear weapons unlawful.
The first is the prohibition on the intentional targeting of non-combatants. Under international law, combatants may never target non-combatants. A nuclear attack on a city for the purpose of destroying the civilian population is thus a clear-cut violation of the laws of war. That means a North Korean nuclear attack on American cities—or an American nuclear attack on North Korean cities—would unquestionably violate the laws of war.
The second is the prohibition on indiscriminate attacks. A fundamental principle of the laws of war is that attackers must make a reasonable effort to distinguish between combatants and non-combatants. If the attacker fails to distinguish between combatants and non-combatants, then the attack is unlawful, regardless of whether the attack is conventional or nuclear in nature. The ban on indiscriminate warfare is particularly crucial in the context of nuclear weapons, which by their very nature inflict indiscriminate destruction on a massive scale.
The Hiroshima and Nagasaki Examples
History provides a grim illustration of how the first two cornerstone principles of the laws of war apply to nuclear weapons. The only country to use nuclear weapons in wartime is the United States. In August 1945, during the final days of World War II, the United States attacked the Japanese cities of Hiroshima and Nagasaki with atomic bombs, attacks that killed a combined total of more than 100,000 civilians. In addition, thousands of Japanese civilians suffered from horrific burn wounds and radiation sickness.
Although the laws of war were not fully developed in 1945, international law as it exists today would deem the Hiroshima and Nagasaki attacks clear-cut war crimes.
First, the United States specifically intended to kill Japanese civilians on a massive scale for the purpose of shocking the Japanese government into surrender. Hiroshima and Nagasaki thus constituted textbook examples of the intentional targeting of non-combatants, which is the most heinous war crime of all.
Second, even if we accepted the completely implausible and untenable argument that the atomic bombs were “merely” intended to destroy Japanese military facilities in Hiroshima and Nagasaki, the American attacks were still unlawful (at least under the current laws of war) because they were indiscriminate in nature. The United States detonated the atomic weapons about 2,000 feet above the Japanese cities, creating blast waves that simultaneously and indiscriminately killed and injured combatants and non-combatants alike. To put it mildly, no effort was made by the United States military to distinguish Japanese combatants from Japanese non-combatants. Consequently, the atomic bombs employed against Hiroshima and Nagasaki were by their very nature “indiscriminate” in character, and therefore undeniably unlawful under the modern law of armed conflict.
The Collateral Damage Conundrum
The illegality of using nuclear weapons in urban areas is thus clear. But is any use of nuclear weapons permissible under international law?
The answer, at least arguably, is yes. In the preeminent textbook on the laws of war, The Conduct of Hostilities under the Law of International Armed Conflict, Prof. Yoram Dinstein points out two potentially lawful uses of nuclear weapons: a nuclear strike on an army convoy in a vast desert far from civilian populations, and a nuclear strike on navy vessels in a remote location in the ocean. In both cases, the targets would be lawful, and the risk to non-combatants would be low. After explaining the legal dimensions of the question, Dinstein emphasizes in his book the inherently destabilizing implications of using nuclear weapons, observing: “All States members of the nuclear club are soberly aware of the colossal ramifications of a decision to unleash these cataclysmic weapons.”
But that point may no longer be so certain. President Trump’s long-standing fascination with nuclear weapons makes it much more conceivable that the United States might actually use nuclear weapons in a confrontation with North Korea. Indeed, as President Trump’s boastful reference to his “nuclear button” suggests, it is at least within the realm of possibility that—in the event of open conflict with Pyongyang—Trump might order a limited, tactical nuclear strike against remote North Korean mountain bases suspected of harboring ICBMs or hydrogen bombs.
The tactical strike scenario implicates a third cornerstone law of war principle: proportionality. International law prohibits attacks that are likely to cause disproportionate “collateral damage," a euphemistic term for unintended death and destruction inflicted on non-combatants. Collateral damage is not inherently unlawful. The critical legal question in such cases is whether the anticipated collateral damage is “excessive” in relation to the military necessity of the attack. In addition, even if the expected collateral damage is proportional to the military necessity of the attack, the attacker must take reasonable precautions to minimize the likely harm to non-combatants.
The problem, however, is one of evidence. The task of proving that collateral damage is "disproportionate" to the military necessity of the attack is exceedingly difficult. The terms “military necessity” and “proportionality” are so subjective and so vague that successful prosecutions for “excessive” collateral damage are few and far between. As Prof. Valerie Epps argued in an important law review article, the collateral damage rule has proven so ineffective that it is almost a dead letter.
The collateral damage issue would be raised because even in a remote location, there would inevitably be at least some civilians killed in the general area by the detonation of a nuclear weapon. But it seems likely that in the event of a tactical nuclear strike on a remote North Korean missile base, the Trump Administration would argue that the “military necessity” of destroying North Korea’s nuclear weapons program is proportional to the anticipated collateral damage caused by the attack. The North Koreans would of course disagree, but there is no objective measure for resolving such a dispute.
The bottom line, therefore, is if President Trump used nuclear weapons against Pyongyang or other North Korean cities, the attack would clearly be unlawful. The same would also be true of a North Korean attack on American cities.
But if President Trump used tactical nuclear weapons against North Korean missile or weapon facilities in remote parts of the country, the laws of war provide very little clarity on whether such an attack would be lawful.
The legal issues notwithstanding, one point should be clear: any use of nuclear weapons would have dangerously destabilizing effects that would be impossible to contain. Presidents have understood that crucial point since at least 1949, when the Soviets developed an atomic bomb of their own, thus ushering in the nuclear arms race of the Cold War era. But whether President Trump understands the destabilizing consequences of using nuclear weapons is a disturbingly open question.
The 1980 ICBM Explosion in Arkansas
Even assuming a peaceful resolution of the U.S.-North Korea standoff is achieved, the mere existence of nuclear weapons poses a significant risk to all countries that have them.
Last year PBS’s American Experience program aired a chilling documentary on the most serious nuclear missile accident in American history. In September 1980 a U.S. Air Force maintenance crew at an underground launch silo in Arkansas accidentally punctured the fuel tank of a Titan II nuclear missile with a 9-megaton warhead onboard. As it became clear that the missile would eventually explode, the Pentagon faced the appalling possibility that the warhead would detonate and destroy much of Arkansas and Missouri.
In riveting and unforgettable fashion, the documentary relates what happened before, during, and after the missile explosion.
Although I don't recommend watching it before going to bed, the documentary, which is based on Eric Schlosser’s important and timely book on the subject, Command and Control: Nuclear Weapons, the Damascus Accident, and the Illusion of Safety, is available on YouTube. It provides a sobering reminder of how profoundly dangerous it is for humans to possess nuclear weapons, let alone use them.