Tensions on the Korean Peninsula have risen quickly this week on the heels of another long-range missile test, combined with public revelations that the Kim Jong-un regime may have miniaturized a nuclear weapon that can be mated to such a missile. If the North Koreans have also managed to solve the other significant challenges associated with a viable intercontinental ballistic missile (ICBM)--which is not at all certain--then they will have achieved an embryonic operational capability.
We knew this was coming. Yet now that the rhetoric is running high, many are concerned that we are on the brink of nuclear war. Even though the possibility of such a war is remote, it has evoked understandable curiosity among the public regarding how the U.S. chain of command would function for ordering a nuclear strike, and whether or not sufficient checks and balances exist to prevent a costly mistake.
On the face of it, it's actually very simple: The president orders the strike, which is then passed to the secretary of defense, and directly to the appropriate four-star combatant commander (the chairman of the Joint Chiefs of Staff is in the loop to provide advice and transmit orders, but he is not technically in the chain of command). In the case of a nuclear strike against North Korea, the commander of United States Strategic Command, based at Offutt Air Force Base in Nebraska, would likely be the responsible commander (a conventional strike would likely be conducted by the commander of United States Pacific Command).
The nuclear forces at the president's disposal would include submarine-launched ballistic missiles, land-based ICBMs, and bombers carrying either cruise missiles or gravity bombs. Each leg has its pros and cons in terms of responsiveness, weapon size, survivability, flexibility, and perception from key nations, among other factors.
President Donald Trump could order a strike either in response to an actual North Korean attack or as a preemptive action.
In the former case, when the U.S. or an ally is actually under attack, a well-developed process exists by which the president is quickly connected to a secure conference call with his senior advisors and supporting personnel. The conference would provide the full range of intelligence information and advice on strike options, as well as other information such as the expected number of casualties and the extent of fallout. Among other legal questions, the necessity and proportionality of the response will come under heavy scrutiny. While any president will always want more time to refine his decision (including to consult with advisors and foreign counterparts), his decision time will be compressed if it appears a follow-on attack is imminent or the president himself is targeted.
A preemptive strike would be a much different animal, involving complex domestic and international legal questions.
Regarding international law (which the U.S. helped put into place after World War II), the U.S. generally recognizes three scenarios under which the use of military force on the territory of another state is permissible: authorization through a United Nations Security Council resolution; a determination of legitimate self-defense (including collective self-defense with allies or partners), which can be in response to the imminent threat of an attack; and use of force in an otherwise lawful manner with the consent of the territorial state.
The word "imminent" is both important and hotly contested in legal circles--the rationale must be clearly justifiable to the international community after the fact. It would be hard to make the case that a North Korean verbal threat is evidence of an imminent attack. With more compelling evidence, the U.S. would presumably argue that the use of force is lawful in order to disrupt an imminent attack by North Korea, but the bar would be very high for a preemptive nuclear strike.
Regarding domestic law, the Justice Department has over the years concluded that the president has the power under the Constitution to take military action abroad for the purpose of protecting important national interests even without specific prior authorization from Congress (though the department has also acknowledged that a pre-planned military engagement that constitutes a "war" may require prior congressional authorization). There are a number of gray areas in the law, and presidents have generally pushed the limits of what they can do without congressional involvement.
For example, the Justice Department has generally found that many recent military operations engaged in by presidents of both parties did not constitute "wars." It seems likely (speaking as a non-lawyer) that the administration would argue that a preemptive strike intended to avoid an imminent attack does not constitute a "war" and can be conducted by the president without prior congressional approval. But, again, the bar would be seem to be high for a nuclear strike.
All of this has raised the hypothetical question of whether or not someone in the chain of command could refuse an order to conduct a preemptive strike. No one is above the law. Members of the chain of command should insist on clear domestic and international legal rationale for such a strike, especially one involving nuclear weapons. If the rationale clearly stands at odds with the law, the chain of command would have the right and the duty to at least consider declining the order.
Fortunately, this scenario is extremely unlikely--there is a big difference between emotionally charged rhetoric and a preemptive nuclear strike. With his current national security team, the president should have the benefit of good, sober operational and legal advice. The more urgent task is finding a viable, multi-national, enduring policy path that leverages all instruments of national power, restores stability on the Korean Peninsula, and minimizes the potential for an unnecessary conflagration in the region.
Admiral James "Sandy" Winnefeld was the ninth vice chairman of the Joint Chiefs of Staff when he retired from the U.S. military in 2015. He previously served as the 21st Commander of the North American Aerospace Defense Command (NORAD). He currently serves as distinguished professor of international affairs at Georgia Tech and as a senior non-resident fellow at Harvard University’s Belfer Center.