Update August 26, 2015
UPI reported along the lines that it is unclear how many North Korean submarines have re-emerged. "Seoul's military said the latest North Korea buildup provided new insight into how Pyongyang would launch an attack on South Korean territory. [North Korean] Submarines would be used to deploy Special Operations personnel to lay mines in South Korean port cities like Busan and Ulsan in order detonate nuclear power plants and other facilities.
News that 70% of North Korea's submarines have submerged and cannot be detected may or may not be significant. North Korea is estimated to have:
- 40 x 300-ton Sangeo-class mini-submarines N Korea's largest known domestically built submarine. The 40 Sangeos represent more than half of North Korea's submarine force of 70.
- 10 x 130-ton Yeoneo-class mini-subs and
- 20 x 1,800 ton 1950s vintage Romeo-class which would probably be only semi-functional .
- 1 SINPO class submarine (up to 1,800-tons) which may be one of the Romeos with one or two vertical launch tubes fitted for future missile use.
If all 50 of the Sangeo + Yeoneo mini-submarines have submerged/disappeared then that is 71%. So perhaps none of the Romeo's, requiring much larger crews, have submerged?
The mini-submarines have only a limited endurance (perhaps 1 week or 2?) so they will need to resurface soon.
Shin Hyon-hee of the The Korean Herald reported late on August 23, 2015 http://www.koreaherald.com/view.php?ud=20150823000453:
N.K. beefs up frontline forces
The Koreas’ cross-border standoff showed more signs of flaring up on Sunday as the North Korean military sharply beefed up its frontline artillery forces and [allegedly] forward-deployed a majority of its submarines and other offensive assets despite the high-level talks over the weekend.
...The South’s military was also unable to locate about 50 undersea vehicles, or 70 percent of the North’s submarine fleet, which have left their bases.
...In particular, the movement of North Korean submarines is a critical indicator of provocation that Seoul closely keep tabs on at all times, he noted.
...“It’s around 10 times the usual. We have not seen in decades that many submarines that are simultaneously out of their bases,” the official said.
“This is the level where we can expect something really worrying to happen ― we don’t know what kind of operations they are and will be undertaking where.”
...The heavily militarized [North Korea] is believed to run more than 70 submersibles including 20 1,800-ton Romeo-class, 40 300-ton Sangeo [or Sang O] class and 10 130-ton Yeoneo [or Yang O] class vessels. Albeit old and equipped with outdated weapons, they outnumber the South’s fleet.
...To head off any unanticipated provocation, the South Korean military is maintaining full readiness and mobilizing more antisubmarine assets such as destroyers, P-3C patrol planes and Lynx antisubmarine helicopters, the official added.
The South Korean Navy operates a 13-submarine fleet, consisting of nine 1,200-ton 209-class and four 1,800-ton 214-class. It is pushing to add five 214-class submarines by 2019 and nine 3,000-ton submarines carrying vertical launchers for submarine-to-ground missiles. It launched a submarine force command last February to better counter North Korean threats and carry out underwater operations, training and education, and maintenance...."