Reports indicate that South Korea is building their locally designed, 3,000 ton, Jangbogo III class diesel-electric submarines with ballistic missile launching capabilities. We already know this new design has a vertical launch system, and while there were rumors it would have short-to intermediate-range ballistic missile launching capabilties, most believed the system was meant to accommodate only land-attack cruise missiles.

The Jangbogo III class represents the final installment of a three class submarine modernization initiative, dubbed the “Korean Attack Submarine Program,” begun more than a decade ago. The first step in this process was upgrading nine existing derivatives of the 1,200 (post mid-life hull stretch 1,400) ton German Type 209 boats that were commissioned in the 1990s. The second step was to produce a variant of the 1,800-ton German Type 214 Air Independent Propulsion-equipped submarine under license. This effort is still underway with four out of nines boats currently commissioned.

The final class, which will dwarf both of its progenitors, is dubbed the Jangbogo III. It is a unique, non-licensed design that uses indigenous technologies almost exclusively, and will be equipped with the latest lithium-ion battery-based Air-Independent Propulsion. Construction of the first of this ambitious class began just last month.
A Republic of South Korean Navy Type 209/Jangbogo I class submarine., US Navy
Apparently, South Korea’s move to equip its new submarines with ballistic missile capability is a response to North Korea ongoing nuclear weapons program and their own submarine-launched ballisitic missile initiative, one that the Hermit Kingdom has made significant progress on as of late. The addition of this capability could also explain why South Korea plans to increase the size of the second boat in the class by some 400 tons.

Still, why would South Korea really need this capability at all? It already has a conventional second-strike capability, via its submarine-launched cruise missiles, and the country is not a nuclear power. Plus, South Korea is already protected under America’s nuclear umbrella.

It is true that even a conventionally tipped ballistic missile is tougher to defend against and hits much harder than an air-breathing cruise missile. Maybe South Korea sees the capability as a unique conventional second-strike deterrent. after all, ballistic missiles are more capable than cruise missiles of destroying deeply-buried North Korean bunkers. This capability could make the North Korean regime more vulnerable to a decapitation strike. Then there’s the possibility that South Korea is baking future nuclear ambitions into its submarine designs.
A South Korean Type 214/Sohn Won-Yil class submarine., Republic of Korea Armed Forces

As the North Korean nuclear threat grows, and as the American presidential campaign floats potential changes in America’s military presence in the region, South Korea could make a grand strategic pivot and begin developing its own nuclear weapons. The ability to slap a few nuclear warheads onto a ballistic missile and load them into an advanced, long-diving submarine is one very powerful way to independently deter a North Korean nuclear attack—with or without America’s nuclear umbrella overhead.

The Korea Herald reports that this new class will be equipped with six vertical launch tubes capable of firing the modern Hyunmoo-2B ballistic missile. The missile in question has a range of about 300 miles and can pack up to a 2,200lb warhead, although under current restrictions it is likely a 1,000lb warhead would be fitted which would maximize the missile’s potential range. Either way, such a weapon should be more than capable of delivering a nuclear warhead if one were developed and deployed by South Korea.

If South Korea does plan on pairing its new advanced and super-sized diesel-electric submarines with the ability to sling hard-hitting ballistic missiles it is likely an ominous sign of things to come. Basically South Korea could be setting itself up perfectly with a delivery system and a near ideal second-strike platform if North Korea continues to progress in its nuclear and submarine-launched ballistic missile program.

Now how the US would react to a South Korea that decides to become a nuclear power is a whole other story.

The inclusion of this type of weapon on a modern AIP –capable diesel-electric submarine is also just another step that further blurs the lines in capability between nuclear and these ever more capable conventionally powered boats.