The issue of nuclear deterrence in the Korean peninsula is usually posed in terms of how reliably the United States and its key regional allies can deter an attack by North Korea. That has it exactly the wrong way around. The question is not whether the US can deter North Korea; that’s a triviality. The real question is whether North Korea can deter the United States.
As I’ve explained at length before, strategic nuclear deterrence is extraordinarily stable when both sides enjoy an assured second-strike capability, ie the ability to retaliate with a devastating counterblow after having absorbed a massive first-strike. Under highly asymmetric conditions, nuclear deterrence is much less stable. If the stronger party can expect a splendid first-strike to destroy the deterrent of the weaker party with certainty, it is hard to see how the latter can deter the former. Of course, certainty is unachievable in practice. The question is just how certain the stronger party has to be for deterrence to fail. Of all the asymmetric deterrence scenarios, the confrontation between the unipole and North Korea is arguably the most one-sided. If North Korea can deter the United States, then deterrence is unlikely to fail anywhere else as well.
So does the United States enjoy nuclear primacy over North Korea? Concretely, if President Trump demanded a military solution to the “problem”, will the generals be able to put forward a viable operational plan to disarm North Korea without exposing the United States and its allies to catastrophic risk? Can the US take out the entire North Korean arsenal in counterforce strike before they have a chance to retaliate?? As usual, the devil is in the details.
The United States would enjoy nuclear primacy over North Korea if it could be near-certain of destroying North Korea’s nuclear capabilities in a splendid first-strike, or if it could be near-certain that it will be able to intercept North Korean missiles before they stuck populous cities and strategic bases of the United States and its regional allies. So we need to evaluate the capabilities of the both the United States and North Korea. Moreover, in order to assess the likelihood of deterrence failure, we also need to assess the balance of resolve. Having a first-strike capability is one thing; having the willingness to carry out a splendid first-strike quite another—much more is involved than simply hard power capabilities.
According to US intelligence, North Korea has an arsenal of some 60 odd nuclear warheads. More importantly, in the assessment of the intelligence community, North Korea has achieved miniaturization, ie they have figured out how to make the warheads small enough to mount them on an intercontinental ballistic missile (ICBM). The beleaguered state’s gains in missile knowhow have also crossed a critical threshold. In the assessment of analysts at the Middlebury Institute of International Studies, the July 4 test launch suggested that the missile had a range of 10,000km, putting the US west coast and midwest within reach. On July 28, North Korea fired a second test missile in a near-vertical trajectory that reached an altitude of 3,500km before falling harmlessly in the Sea of Japan. Analysts reckon that even New York, Boston and DC are now within operational reach of North Korean missiles. It’s still not clear whether they have figured out how to ensure that the warhead doesn’t burn up upon reentry into the dense lower atmosphere. It shouldn’t take long for them to achieve that capability. In any case, US strategists must assume that the North Koreans have the capability to strike the most populous US cities and, a fortori, US military bases in the region and the cities of its regional allies.
Can the United States be near-certain that its theater and intercontinental missile defense systems will be able to intercept North Korean missiles? The short answer is no. Of the last 5 tests of the ICBM ballistic missile defense system, 3 have failed. Theater missile defense (TMD) may perform better under test conditions, but is likely to fare even worse under actual warfighting conditions because North Korea has many more short-range platforms to strike Japan and especially South Korea (where it can even use artillery to deliver nuclear payloads) and they can deploy many more decoys to distract the systems. North Korea also has electronic warfare capabilities that can potentially interfere with TMD systems.
On the other hand the United States has a formidable repertoire of counterforce capabilities. The United States can use low-orbit platforms like satellites, air-breathing unmanned platforms (ie surveillance drones), and manned fixed-wing aircraft to generate near-continuous targeting solutions. The US can utilize a full-spectrum of air-, land- and sea-based launch platforms to take out North Korean targets. Lieber and Press (2017) have shown that North Korea would find it hard to ensure the survivability of its nuclear deterrent against the United States since the US can substitute seamlessly between multiple platforms for cueing, targeting, and strike solutions (“fire-control solutions”). In other words, the United States enjoys nuclear primacy over North Korea in the sense that the US can carry out a splendid first-strike against the North Korean arsenal with near-certainty.
But the problem is that the balance of resolve favors North Korea. No conceivable interest of the United States or its regional allies can be served by exposing themselves to North Korean nuclear strikes even an iota. Even though the US could take it out on demand, the very existence of the North Korean deterrent means that Japan and South Korea would resist a preemptive strike against North Korea. US assurances that the risk is small are quite unlikely to satisfy Seoul and Tokyo. Both allies would expect compelling reasons why they must run even a small risk of a nuclear attack.
Put another way, the United States is deterred because North Korea hasn’t raised the stakes enough to threaten a vital interest of South Korea and Japan. It is in the US interest to prevent a North Korean deterrent capable of striking US cities. But the US would find it impossible to convince Seoul and Tokyo that they need to run the risks necessary to achieve that goal. The United States cannot find a persuasive reason because there isn’t one. So much for nuclear primacy.