North Korea's submarine missile firing raises the nuclear stakes

North Korea’s recent test of a submarine-launched ballistic missile (SLBM) marks a dangerous turning point for its nuclear program. An SLBM capability will give North Korea an almost invulnerable second-strike capability, which will limit the options for the United States and allies such as South Korea and Japan to manage North Korean threats. This may then embolden North Korea to undertake more aggressive behaviour, demonstrating the seriousness of this development.

The test: success or failure?

This latest test reveals that North Korea has developed a preliminary capability of performing submerged launches of missiles. According to South Korean officials, the missile flew only about 150 metres from the point of launch. This has led some to speculate that the test resulted in failure.

Unfortunately, this conclusion reflects a dangerous misunderstanding of the test and of North Korea’s intentions regarding its nuclear deterrent. This misunderstanding is a result of the assumption that this was a flight test of the missile. The purpose of a flight test is to determine whether a missile is capable of reaching its design objectives of speed, altitude, range, payload etc.

However, this was most likely not the purpose of this test. Rather, North Korea was almost certainly conducting an ejection test of the missile. This sort of test enables any issues to be thoroughly ironed out before conducting a proper flight test.

SLBMs are ideally fired while the submarine is submerged, to avoid detection pre-launch. To accomplish this, the missile must first be ejected from the submarine, before the rocket motor ignites (which would destroy the submarine if this occurred while the missile was still inside).

The purpose of an ejection test is to determine whether the ejection system and the rocket motors are sufficient to launch a missile from underneath the ocean surface. This latest test achieved this objective. Thus, the missile flying only around 150 metres is irrelevant.

Of course, this does not indicate that North Korea is ready to deploy SLBMs operationally. What is does does reveal is that its missile program is perhaps developing more rapidly than previously thought.

Why SLBMs alter the nature of the threat

This test is the latest indication that North Korea is not content with a crude and limited nuclear arsenal. Rather, it is seeking to become a legitimate nuclear power, with a large, functional and survivable nuclear arsenal covering a range of uses, from front-line battlefield use to strategic deterrence. Given North Korea’s belligerent and often dangerous behaviour, this is a concerning development.

An SLBM capability raises the stakes in regard to the threat posed by North Korea’s nuclear program, not only to states in the region such as Japan and South Korea, but also to the US. Indeed, even China is growing concerned about the threat posed by North Korea’s nuclear arsenal.

Submarine-launched missiles are particularly dangerous because of the difficulty in detecting them until they are fired.Flickr/US Pacific Fleet, CC BY-NC

The reason that North Korean SLBMs would be particularly dangerous is that they are nearly invulnerable to pre-emptive strikes. That is the entire point of North Korea seeking such a capability. While North Korea’s submarines are inferior to modern Western designs, making them relatively easy to detect and track, even a single submarine that manages to escape detection would pose a significant threat.

The dangers are further enhanced when it is considered that North Korean subs may be able to approach close to the coastline of a target country before launching their missiles. This would drastically reduce the warning time for missile defences to detect and engage the incoming missiles.

Furthermore, unlike North Korea’s current and rather crude land-based missiles, it would be almost impossible to detect pre-launch preparations. The first warning of an impending North Korean ballistic missile attack originating from a submarine would be when radar detects the missile in the air.

How might the US and its allies respond?

The increased threat posed by the above scenario will only serve to harden the resolve of the US and its allies. This may well increase the chances of US-led pre-emption, before this option becomes unviable. If the North does manage to deploy nuclear-armed SLBMs, the value of the pre-emptive strike option is substantially diminished, as North Korea would possess the means to launch a guaranteed nuclear retaliation in response to any hostile action against it.

Additionally, the possibility of enhanced North Korean aggression if it feels more comfortable that at least some of its warheads are secure from pre-emptive strikes may push South Korea to adopt US-designed missile defence systems. Seoul is considering the purchase of terminal high-altitude area defence (THAAD) systems. The pressure created by increased North Korean capabilities may lead South Korea to conclude that it needs to deploy these systems.

If this occurs, it may well lead to an offensive and defensive arms race on the Korean peninsula, with North and South Korea vying to gain an advantage. This would only succeed in decreasing security and increasing the likelihood of conflict on the peninsula. That is a deeply worrying thought when one of the actors is a nuclear-armed state with a history of belligerent behaviour.

This test of a submarine-launched ballistic missile was not a failure, but an indication that the North Korean nuclear program is rapidly advancing. If North Korea manages to successfully field SLBMs, then it will possess a virtually invulnerable second-strike capability, decreasing the ability of the US and its allies to engage successfully in pre-emptive strikes should the need arise.

Given this, the US and South Korea may well be encouraged to pre-emptively attack North Korea’s nuclear and strategic assets before this option becomes unavailable. The hardening of US resolve may well backfire for North Korea, which may ironically decrease its security through attempting to increase the credibility of its deterrent.

James Dwyer does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.