July 7, 2019: In June 2019 South Korea completed another refurbishment for the Na Daeyong, one of its nine German Type 209 subs. The work on this one took two years and involved installing new electronics as well as a towed array sonar. The refurb makes this boat, which entered service in 2000 capable of serving into the 2030s. These boats, except for the first one, were built in South Korea by South Korean personnel who had gone to Germany to assist with the construction of the first one. These boats, are the Chang Bogo, or KSS-1, class that entered service between 1993 and 2001. Each has undergone refurbs, taking one or two years, every eight to ten years. The latest Na Daeyong refurb was very extensive turning this boat into a formidable ASW (anti-submarine warfare) system. The Chang Bogos began as modified Type 209s and kept evolving. Germany was always willing to modify exported subs for customers and since, South Korea licensed the 209 design and built eight in South Korea, each Chang Bogo became unique as they underwent first one then a second refurbishment. The multiplicity of modifications enabled the navy to experiment with new features and South Korea shipbuilders gained practical experience implementing all the changes.

All nine Chang Bogos will remain in service until at least 2025 and probably later. Much depends on what threats the North Korean and Chinese navies pose. The Chang Bogo upgrades usually include new equipment and capabilities as well as more modern versions of original components. For example, South Korea is replacing the original batteries with more powerful lithium ion type batteries that were designed for submarine use. All Chang Bogos are believed now able to use the torpedo-tube launched Harpoon anti-ship missile and much upgraded passive sensors.

The Chang Bogos began as 1,200 ton boats that are 55.9 meters (174 feet) long, have a top speed while submerged of 39 kilometers an hour, and a top surface speed of 20 kilometers an hour. Range is 20,900 kilometers at a surface speed of 7.4 kilometers an hour. Endurance is 50 days and the highly automated boat has a crew of only 31. Armament is 14 torpedoes fired from eight 533mm (21 inch) tubes. Chang Bogos have become a little longer and heavier because of extensive refurbs. South Korea intended to export subs as well and found an eager customer in Indonesia.

In 2016, after 13 years of negotiations, delays and finally construction Indonesia has launched the first of three Chang Bogo class subs. This first one entered service in 2017 followed by the two others in 2018 and 2019. The third boat was built in Indonesia with South Korean help. Two older Indonesian Type 209s (built in Germany), were refurbished by South Korea, a job that was completed in 2011. Indonesia was a happy customer and in 2019 agreed to buy three of the new South Korea Type 214 subs.

South Korea licensed and modified the German Type 214 sub design and began building them in 2006 with the first (Sohn Wonyil) entering service in 2007. South Korea has seven of nine new Type 2014 submarines as of 2018 with the other two due in 2020. A third class, the KSS-3, is a 3,300 ton high seas boat and first of four is to enter service by 2022. These boats have AIP (air independent propulsion), a crew of fifty and are armed with eight 533mm torpedo tubes, four of them capable of launching Harpoon anti-ship missiles. KSS-3 will also have ten VLS tubes for cruise missiles. If all this sounds like a smaller, non-nuclear, version of the American Virginia class SSNs (nuclear-powered attack sub) it is. The Australians pioneered this approach with their six Collins class boats that began entering service in 1996. The 3,100 ton Collins class subs had 70 days endurance and were meant to operate over vast distances in the Pacific Ocean.

South Korea has been upgrading its submarine force for some time now. The Type 214s are known as KSS-2 class boats while the Type 209s are KSS-1 class subs. These KSS 2 class subs are armed with South Korean made Haeseong-3 cruise missiles and torpedoes. The Haeseong-3 is like the torpedo tube launched American Tomahawk. Haeseong-3 has a range of 1,500 kilometers and can reach any target within North Korea.

The first three KSS-2s were built (from German components) by Hyundai Heavy Industries, one of the two South Korean firms that builds subs. Much to the chagrin of South Koreans, who are trying to develop their own submarine design and construction capability, the first three Type 214s had quality problems. Mostly it was because of defective components and poor construction techniques that left the three boats noisy and easier to detect. The first three Type 214 subs were out of action for most of 2010 because of these problems. This was very embarrassing, as these subs were built in South Korea and that was a big deal for South Koreans. Building submarines is a very specialized and exacting type of manufacturing and South Korea has only been doing it only since 2000. The defects in the South Korean built sub were traced to bolts, made by a South Korea firm but not to the original German specification. The Germans worked with South Korea sub builders to improve South Korean quality control procedures to avoid that sort of thing.

South Korea went ahead with plans to build six more Type 214 subs. The Type 214 boats used AIP based on fuel cells, enabling them to stay underwater for up to two weeks, which is ten times longer than the Type 209s. The Type 214 is a 1,700 ton, 65 meter (202 foot) long boat, with a crew of 27. It has four torpedo tubes and a top submerged speed of 35 kilometers an hour. Maximum diving depth is over 400 meters (1,220 feet).

AIP boats go for up to a billion dollars each. The second batch of South Korean 214s have an improved AIP system, which is apparently more reliable and provides a small increase in time underwater. South Korea wants to become a supplier of AIP systems as well because they now have the industrial expertise for this sort of high tech. The latest Type 214 boat is important because if it proves to be flawless, it will make South Korea a contender in the international submarine market. Potential export customers, largely from East and Southeast Asia, are already showing interest.

The growing South Korean submarine force (nine Type 209 and nine Type 214s by 2020) has become a major part of the fleet. In recognition of this in early 2015 South Korea created a new Submarine Command whose main purpose is to develop better anti-submarine capabilities against North Korea or even China.

Another reason for the Submarine Command was to make it easier to curb the procurement corruption that has developed in the navy. Several senior navy officers and officials have recently been prosecuted for this sort of misbehavior. Since the submarine service is rather elite and much more sensitive to getting the most for their money, the Submarine Command, run by submarine officers, is expected to be more resistant to corruption. That is important because South Korea is putting a lot more money into submarines.

The main threat is seen as the very modern and growing Chinese fleet but for the moment North Korea is considered more dangerous. The North currently has 70 subs, but most (over 70 percent) of them are very small (and often elderly) coastal types. There are twenty larger (1,800 ton) Romeo type boats but these are also very old, noisy and easy for other subs to detect under water. North Korea is building at least one diesel-electric sub that can launch ballistic missiles.