North Korea Launches Strategic Cruise Missiles from Submarine

On Sunday, North Korea launched two cruise missiles from a submarine in the waters near the country’s eastern port city of Sinpo. The submarine missile launches came right before the United States and South Korea kicked off their planned Freedom Shield (FS) exercises, which will last for 11 days until March 24. Earlier this month, North Korea vehemently criticized ongoing U.S.-Republic of Korea (ROK) joint military drills, which it claims as a rehearsal for invasion. Yesterday’s submarine-launched cruise missile (SLCM) test came a day after Kim Jong-un warned of North Korea’s "important practical measures” to enhance its war deterrence against the resumption of large-scale FS exercises, which will involve about 20 field exercises this year including amphibious landings.

Q1: What is the significance of North Korea’s cruise missile test launches from a submarine?

A1: This is the first time that North Korea test-fired “strategic cruise missiles” from the 8.24 Yongung (August 24 Hero) ballistic missile submarine. According to North Korea’s state media, the cruise missiles flew nearly 1,500 km (932 miles) and successfully struck an underwater target. If North Korea’s claim is true, this indicates that entire South Korea and possibly the U.S. Kadena airbase in Okinawa, Japan, where U.S. F-22s fighter jets are stationed, could be within North Korea’s target range. In addition, the country’s successful SLCM test implies North Korea’s improved ability to further complicate the allied missile defense system because the cruise missiles are much more difficult to intercept given their complex flight trajectories. And, most importantly, the SLCM test, if proven successful, shows North Korea’s credible second-strike capability as the country continues to strengthen its nuclear deterrence.

Q2: Why did North Korea conduct SLCM tests?

A2: North Korea’s new SLCM tests appears intent to demonstrate the country’s advancing and diversifying naval second-strike capability. With its successful test of Pukguksong-1 in August 2016, North Korea already possesses the submarine-launched ballistic missile (SLBM) capability although the estimated range of the latest Pukguksong-3 SLBM test in October 2019 was about 1,900 km (1,200 miles) if launched on a normal trajectory. North Korea’s SLBM program has progressed slowly in comparison to the land-based nuclear ballistic missile program, but the SLBM program manifests the country’s progress in developing a second leg of its nuclear triad (CSIS Beyond Parallel satellite imagery on Shinpo South Shipyard documents the latest development activities). Given this, North Korea’s SLCM test yesterday indicates the country’s effort to demonstrate its varied second-strike capability that would be hard to track, can better survive a first attack, and penetrate the allied missile defense system.

Q3: What will likely happen during the U.S.-ROK FS exercise?

A3: CSIS data shows that North Korea has a propensity to engage in major weapons provocations during the U.S.-ROK joint military exercises when there is no diplomatic engagement between Washington and Pyongyang. North Korea will likely carry out various types of weapon testing and exercises to demonstrate its war deterrence and conduct war simulation drills. As yesterday’s SLCM test shows, North Korea’s new weapon testing could involve an intercontinental ballistic missile (ICBM) test launched at a normal angle. The prospect of the ICBM test toward the Pacific is ominous especially given Kim Yo-jung’s warning in late February that the country could turn the Pacific into its “firing range.” Heightened tension will likely engulf the peninsula as the two Koreas will find it difficult to break away from the action-reaction cycle, as was observed in September and October 2022, which will raise the risk of miscalculation and military accidents.

With President Yoon Suk Yeol scheduled visit to Japan in March 16–17, it is possible that North Korea may carry out a major provocation in time for his visit to spoil the bilateral summit between Yoon and Kishida, which comes in the wake of a breakthrough between South Korea and Japan to resolve the wartime labor issues and improve their constrained bilateral relationship.

Ellen Kim is deputy director and senior fellow of the Korea Chair at the Center for Strategic and International Studies in Washington, D.C.