North Korea is powerless to prevent a U.S. strike on its nuclear program, but retaliation is well within its means. The significant military capability that North Korea has built up against South Korea is not advanced by Western standards, but there are practical ways Pyongyang could respond to aggression.

The North Korean military’s most powerful tool is artillery. It cannot level Seoul as some reports have claimed, but it could do significant damage. Pyongyang risks deteriorating its forces by exposing them to return fire, however, which significantly restricts their use. Less conventional methods of retaliation, such as sabotage or cyber warfare, are less risky but also limit the shock that North Korea would desire.

After a strike, North Korea’s most immediate and expected method of retaliation would center around conventional artillery. Many of the North’s indirect fire systems are already located on or near the border with South Korea. By virtue of proximity and simplicity, these systems have a lower preparatory and response times than air assets, larger ballistic missiles or naval assets. Nevertheless, there are several critical limitations to their effectiveness.

Tube and Rocket Artillery

The biggest anticipated cost of a North Korean artillery barrage in response to an attack would be the at least partial destruction of Seoul. But the volume of fire that the North can direct against the South Korean capital is limited by some important factors. Of the vast artillery force deployed by the North along the border, only a small portion — Koksan 170-mm self-propelled guns, as well as 240-mm and 300-mm multiple launch rocket systems — are capable of actually reaching Seoul. Broadly speaking, the bulk of Pyongyang’s artillery can reach only into the northern border area of South Korea or the northern outskirts of Seoul.

All forms of North Korean artillery have problems with volume and effectiveness of fire, but those issues are often more pronounced for the longer-range systems. Problems include the high malfunction rate of indigenous ammunition, poorly trained artillery crews, and a reluctance to expend critical artillery assets by exposing their positions.

This is an extreme scenario, however, and one in which North Korea chooses to expose all of its most advanced rocket artillery systems simultaneously, suffers no failures, and chooses to direct all of them against Seoul itself. Yet in northern parts of Seoul, well within range of Koksan 170-mm self-propelled guns and 240-mm multiple rocket launchers, a more intense volume of fire could be achieved even if North Korea is prudent enough not to expose all of its capable artillery pieces. Infrastructure damage in Seoul, particularly its northwestern areas, would be difficult to prevent in the event of an immediate saturation of artillery fire. That said, underground shelters and concerted evacuation efforts, which would be initiated immediately in the event of an attack, could greatly reduce civilian casualties. It is also unlikely that North Korean artillery fire would be sustained at great volume. Even an initial mass volley imposes great risk to the artillery systems themselves, making them vulnerable to counter-battery fire. This means casualty rates would drop significantly after the initial barrage, limiting potential civilian casualties to thousands of dead rather than tens of thousands, as has been speculated in some instances.

Ballistic Missiles

In addition to its conventional artillery capabilities, North Korea also has a large stockpile of ballistic missiles with much greater ranges. These missiles vary from older Scud variants to North Korean versions of the Russian-designed system. There are also a number of self-developed longer-range missiles in the North Korean arsenal. Even the lowest-range Scud ballistic missiles would be capable of striking anywhere in South Korea. The main factors constraining the use of these systems, therefore, are volume of fire, equipment failures and depletion of stockpiles.

Even subtracting the most dated portions of the North Korean stockpile — which may not be in operational condition — it still has more than 1,000 ballistic missiles that could strike across South Korea. These range from Scud-based Hwasong missiles to Nodong and Taepodong projectiles. The Hwasong and Nodong missiles are the most important for achieving volume of fire, especially considering North Korea’s limited ability to launch Taepodong missiles. The Taepodong is restrained by Pyongyang’s dependence on large surface infrastructure, found in only two locations in North Korea. The long preparation times before launch make the larger missiles extremely vulnerable to counterstrikes, and the Taepodong does not deliver significant advantages over the Nodong missiles.

When assessing the damage that could be done by North Korean ballistic missile strikes, much depends on how they would be used. In conjunction with conventional artillery strikes, ballistic missiles could provide significant extra firepower directed at Seoul and surrounding areas. North Korea could also use these weapons to expand the indirect fire threat to the entirety of South Korea. This means that there would be less concentration of firepower as a whole but that a diverse spread of locations throughout the country would be subject to infrastructure damage or casualties.

Moreover, ballistic missiles could strike U.S. military positions beyond the Korean Peninsula, specifically in Japan. Whatever the targets, Pyongyang’s existing ballistic missile stockpile could easily deliver approximately 1 kiloton (1,000 metric tons) of high explosives, as well as other nonconventional munitions — chemical, biological or even nuclear. Because of the inaccuracy of different North Korean missile systems, these strikes would most appropriately be used against urban centers or other wide-area targets. If employed against specific military facilities at longer ranges, a significant amount of misses would occur.

As with conventional artillery, North Korea will also be forced to show restraint in the use of these systems. Survivability may be less of a challenge because of the predominance of mobile launcher systems, but unlike conventional artillery munitions, ballistic stockpiles are limited — as is the ability to replenish them, which would draw on significant resources. Every missile spent by North Korea in an immediate retaliation scenario will diminish the leverage it maintains immediately after the retaliation. Furthermore, the high potential for failed launches, as demonstrated by frequent unsuccessful missile tests across a variety of platforms, could further damage Pyongyang’s ability to influence through its ballistic missile stockpile.

The most significant threat from North Korea’s ballistic missile stockpile is the potential for a nuclear strike. Some estimates indicate North Korea may have between two and five nuclear warheads at its disposal already, at least some of which could be made to fit on a Nodong missile. Even a single nuclear strike against a South Korean population center would result in catastrophic shock and incur an immense cost. Though a nuclear strike would not automatically guarantee Seoul’s capitulation, South Korea and the United States factor the possibility of such a strike heavily into their considerations of a strike on the North’s nuclear program.

In the final installment of this series, we will explore other, unconventional retaliatory options open to North Korea and conclude with an assessment of the likelihood and severity of military action against Pyongyang.

Part 1: Assessing the North Korean Hazard

Part 2: Derailing a Nuclear Program by Force

Part 3: What the U.S. Would Use to Strike North Korea

Part 4: How North Korea Would Retaliate

Part 5: The Cost of Intervention