UPI's Elizabeth Shim has reported on January 13, 2021, in part:
South Korea is developing a new submarine-launched ballistic missile [SLBM] and has tested the weapon at the Agency for Defense Development's Anheung test site [just southeast of central Seoul], according to a local press report.
Newsis reported [January 13, 2021] the SLBM was test launched from a ground platform and next-step underwater tests are scheduled for March [2021]. South Korea's military also conducted other SLBM tests in 2020 "several times," both on land and underwater, the report said.
The report of Seoul's domestic SLBM, described as a modified version of Korea's short-range, solid-fueled Hyeonmoo-2B [see Submarine-launched Variat sub-heading 800km range with 500kg payload] ballistic missile,
...South Korean military sources did not deny domestic SLBM development on [January 13, 2021], according to Newsis. Sources told the news service Seoul has "secured hi-tech power" to "support peace on the Korean Peninsula, by building up strong military power," the report said.
In March [2021] Seoul is expected to carry out an underwater SLBM test by deploying a 3,000-ton Dosan Ahn Changho-class [KSS-III] submarine. The South Korean submarine is equipped with six vertical launch tubes that can eject SLBMs..."