North Korea has been repeatedly test-firing submarine-launched ballistic missiles. On Aug. 24, an SLBM launched off Sinpo, a city in northeast North Korea, flying for about 500 kilometers. If fully deployed, these missiles pose a serious security threat to Japan, the United States and South Korea.

North Korea’s SLBM program is steadily progressing. Looking at footage released by North Korea, a missile ignited the moment it cleared the water and flew smoothly. This was the most difficult part, and probably relied on technology provided by the former Soviet Union. North Korea is now able to reproduce that technology.

The SLBM may be the same type as a Musudan medium-range ballistic missile. The Musudan is widely believed to be a variant of the R-27 SLBM purchased from Russia that has been modified for land-based launches. A series of launches have been carried out since spring, and a missile reached an altitude of 1,000 kilometers for the first time in June.

North Korea’s SLBM was launched from a Sinpo-class submarine. Although it was modeled on a Golf-class submarine made in the Soviet Union, the crucial launch equipment was removed prior to purchase. According to US reports, North Korea later purchased missile launch equipment and modified the submarine so that equipment could be installed, creating the Sinpo class.

The submarine’s hull is roughly 6 meters in diameter, and the bridge is about 6 meters high. As the Musudan is about 12 meters long, it can be installed vertically. Therefore, the recently launched SLBM was also likely fired from a Sinpo-class submarine.

Submarine construction is not easy. One of the most important factors is resistance to water pressure. In order to make the hull withstand extreme water pressure, steel plates must be molded into a true circle and welded to avoid leaving any gaps. Only a few countries, including Japan, are capable of building submarines on their own.

The Sinpo class is most likely a battery-powered submarine of about 2,000 tons. It can only dive to shallow depths and operate in coastal waters. I believe it is incapable of venturing far into the Sea of Japan, let alone the Pacific.

Technically speaking, it is virtually impossible for North Korea to send its submarines into the Pacific and approach the US mainland in the near future.

What North Korea wants most is to develop the KN-08 intercontinental ballistic missile, which uses improved technologies from its advanced Taepodong-2 long-range ballistic missile and is capable of reaching the US mainland. If it can do this, North Korea believes it will be on an equal footing with the US in terms of nuclear deterrence.

With Musudans and SLBMs, which are still in an experimental stage, the objective is to achieve a range of 4,000 kilometers. The intended target is not Japan or South Korea, but rather Guam, a strategic base for the US military. It would be sufficient if SLBMs launched off the coast of Sinpo -- like the most recent launch -- could reach Guam.

In terms of nuclear deterrence, the significance of SLBMs lies in their second-strike capability. In other words, even if a country’s ground-based nuclear capabilities are destroyed in a first nuclear strike, nuclear weapons at sea can be used in a second strike against the enemy. Theoretically, this is how they work as a mutual nuclear deterrent.

If North Korea’s SLBMs were to achieve full combat capability, the credibility of the US nuclear umbrella could be undermined. This is because it could lead to such doubts as, “Will the United States really carry out a nuclear strike against North Korea in order to defend Japan?” or “Will the United States hesitate to carry out a nuclear strike against North Korea out of fear that Guam will be hit by a second strike?”

For Japan, the prospect of the nuclear umbrella being disregarded can be considered a threat.

By Toshiyuki Ito

This article is taken from an interview with Toshiyuki Ito conducted by Yomiuri Shimbun senior writer Tatsuya Fukumoto. -- Ed.

(The Japan News/Asia News Network)