On September 8, North Korean media announced that “a Korean-style tactical nuclear attack submarine” had been rolled out of a construction hall at the Sinpho South Shipyard into the water two days before. Associated photos revealed substantial modifications made to an existing old ROMEO-class conventionally powered submarine to launch “tactical nuclear weapons.” The text of a speech Kim Jong Un reportedly gave on the occasion provided further insight into the origin and purpose of the new sub, and North Korean plans for a nuclearized Navy, including further such conversions and a renewed commitment to building nuclear-powered submarines.

There are six key takeaways from the rollout of the “new” nuclear-armed conventionally powered ballistic missile submarine (SSB):

• This is most likely the same ROMEO that was being modified when Kim Jong Un visited in July 2019, which had probably been in the construction hall since 2014. At that stage, the new submarine was expected to be configured to carry three submarine-launched ballistic missile (SLBM) launch tubes. However, extensive modifications appear to have been made after that site visit.
• The most significant remodifications focused on accommodating more missiles. The missile section is much longer, containing four launch tubes for SLBMs of about the same diameter as the 1,250-kilometer (KM) range Pukguksong-1 or 1,900-km range and Pukguksong-3 (which could also accommodate the smaller-diameter KN-23 short-range ballistic missile [SRBM]), and six launch tubes most likely for the 0.5-0.6-meter (m) diameter, 2,000-km-range Hwasal-2 land-attack cruise missile (LACM). The larger tubes could not accommodate the North’s newer, larger Pukguksong-4, -5 and probable -6 SLBMs.
• This shift ’in an SSB’s mission from strategic to “tactical” is consistent with North Korea’s emphasis on “tactical nukes” over the past few years for propaganda and deterrent purposes. The Pukguksong-1, -3, and LACM could cover all of South Korea and Japan, and US bases there, from North Korean territorial waters; the KN-23 would be largely limited to South Korea. Deployment close to North Korea will also be the best way to mitigate the extremely high vulnerability of the old-tech, very noisy sub—increased by the sub’s various modifications—to allied anti-submarine warfare (ASW).
• Kim apparently also intends to convert “all” of the North’s remaining ROMEOs (up to 19) to the new configuration, raising the prospect of a future force carrying up to 80 SLBMs and 120 LACMs. This combination of more subs carrying more missiles is probably North Korea’s best option to obtain a large enough sea-based deterrent to be militarily significant. But it remains to be seen how many ROMEOs are actually converted into missile subs and how long that might take, given North Korea’s limited shipbuilding capacity. Work on future conversions is likely to be slow-going—probably at least five years per boat. Deploying additional road-mobile missiles will almost certainly remain a more cost-effective and more survivable way for North Korea to add to its nuclear strike capability.
• Kim’s vision for the future of the Navy is heavily focused on it “going nuclear,” including explicitly for reasons of cost-effectiveness. This is strangely reminiscent of the Eisenhower Administration’s “New Look” strategy from the mid-1950s that relied on nuclear weapons as a less economically costly alternative to large conventional forces.
• That vision also still includes developing nuclear-powered submarines, to which Kim said, “…we should give greater impetus.” But the speech seems to recognize such a capability will be a long time coming, barring substantial Chinese and/or Russian technical assistance.

The bottom line is that, while the rollout of the larger-capacity SSB and prospect of further conversions provides a credible path for a future (albeit theater-focused) sub-launched missile force, such a force will almost certainly continue to play second fiddle to the much larger, still growing, and much more survivable land-based ballistic and cruise missile force.

Read the full analysis on 38 North.