During his first official trip to Asia last month, President Trump issued a stern warning to North Korea: “Do not underestimate us. And do not try us.” But for his part, Mr. Trump should not underestimate the steep human cost of initiating a war against Pyongyang.
The key problem for the United States is the likely possibility that North Korea has the missiles to deliver nuclear bombs to South Korea and Japan. If one of these weapons were to reach its target, an entire city would be annihilated.
And even if an American first strike knocked out North Korea’s nuclear capacity, millions of South Korean civilians, and American and South Korean soldiers, would be vulnerable to retaliation with conventional or chemical weapons. Pyongyang could devastate Seoul and kill tens of thousands of people.
North Korea may have as many as 250 mobile missile launchers, some of which could fire nuclear-tipped missiles. If some of these mobile units were dispersed at the time of an American attack, it’s unlikely that the United States could destroy all of them before one fires a missile. America has not had much success in finding and destroying mobile missile launchers in recent wars.
An American attack that truly caught North Korea by surprise could minimize the effectiveness of a North Korean counterattack — but not eliminate the possibility. And surprise would be difficult, if not impossible, to achieve.
North Korea probably has reliable intelligence sources reporting on activity in South Korea and Japan that could warn of an attack. And news reports from the United States and elsewhere, or the intelligence agencies of other countries like China and Russia, could also warn Pyongyang.
To plan a surprise, the United States would have to make as few visible preparations as possible. Washington could not significantly increase its forces in the region without raising alarms in the North. The South Koreans would have to be kept in the dark, and they could make no preparations for war. Nor could American civilians be alerted and evacuated from South Korea. Any preparations would have to be masked behind other more normal activities such as training exercises.
But the surprise attack would still require large numbers of powerful, precise, concrete-piercing munitions to destroy the hardened bases that store North Korean missiles and nuclear warheads. Only American strategic bombers — B-2s and B-1Bs, which take hours to reach North Korea from Guam, or longer from bases in the United States — could do this job. And the bombers would require considerable support from aerial tankers.
It is difficult to estimate how many bombers it would take because there is little public information about North Korean military bases. My own estimate, based on marrying published estimates of the number of North Korean missile launchers to past American practice in deploying such systems, is that an initial attack could require at least two dozen bombers, capable of carrying nearly 500 one-ton precision guided bombs, or smaller numbers of larger weapons.
American submarines could move close enough to the North Korean coastline to launch cruise missiles while the bombers are en route. This would minimize the chance that North Korea’s mobile weapons are moved before the bombers arrive and would suppress some of the North Korean air-defense weapons.
But the overall effort would be so large that trying to catch the North Koreans by surprise would be a high-risk gamble. And the first wave of American assaults would have to be focused on attacking nuclear infrastructure, at the expense of dismantling conventional weapons.
Thus, even if an American attack on the North’s nuclear weapons were entirely successful, North Korea would have the opportunity to retaliate with conventional forces against unprepared soldiers and civilians in South Korea. In most scenarios, it is all but inevitable that many thousands of civilians, and American and South Korean soldiers, would die.
A surprise American nuclear attack would offer the greatest chance of eliminating the North Korean nuclear arsenal and of preventing a conventional counterattack. America’s nuclear weapons are quite accurate and always ready for action.
But the detonation of even a small number of nuclear weapons in North Korea would produce hellish results. The United States would make itself an international pariah for decades, if not centuries. It is entirely possible that the American military personnel would even resist the order to execute such an attack. For strategic, humanitarian and constitutional reasons, a first-strike nuclear option should not even be on the table (other than to forestall an imminent nuclear attack from North Korea).
The complexity, risks and costs of a military strike against North Korea are too high. A combination of diplomacy and deterrence, based on the already impressive strength of South Korean and United States conventional and nuclear forces, is a wise alternative.
Barry R. Posen, a professor of political science at M.I.T. and director of its Security Studies Program, is the author, most recently, of Restraint: A New Foundation for U.S. Grand Strategy.