By Jung Sung-ki
The sinking of the naval ship Cheonan last month has placed a renewed spotlight on North Korea's submarine capability, though whether or not the North was linked to the incident has yet to be confirmed.
If North Korea's involvement turns out to be true, the communist state is expected to conduct underwater operations against South Korea more frequently in the future as an effective way of provocation, according to military officials and experts.
``The ROK Navy is definitely dominant now over its North Korean counterpart in terms of surface warships and their radar systems but not sure about underwater competition,'' Park Chang-kwon, a senior researcher at the Korea Institute for Defense Analyses (KIDA), said in a phone interview with The Korea Times. ``That's because there is an inherent restriction on detecting targets underwater.''
High waves and strong currents in the eastern and western waters of the Korean Peninsula, in particular, hamper sonar detection of enemy targets under the water, Park said, raising the need to deploy more advanced underwater detection and coastal surveillance systems.
``North Korean submarines have posed and will pose a grave threat to the security of South Korea both in the peacetime and wartime,'' the researcher said. ``As it has done in the past, the North is expected to continue to use the western waters as a major flashpoint for conflicts with the South."
The North Korean Navy consists of two fleet headquarters in the East and West Sea, 13 squadrons, and two maritime sniper brigades under the Naval Command.
The North's Navy is believed to operate about 650 vessels, including 70 submarines -- 1,800-ton Romeo-class, 370-ton Sang-O (Shark)-class, 90-ton Yugo-class and midget submarines with a weight of five to 10 tons -- which are capable of placing mines and attacking South Korean vessels.
About 60 percent of the vessels are deployed in forward naval bases.
Who's to Blame?
The Romeo class consists of Soviet diesel-electric submarines built in the 1950s.
The North's Navy is believed to operate Romeo-class submarines that are both locally assembled with Chinese parts and directly imported from China.
The 76-meter-long sub can sail at 15.2 knots surfaced and 13 knots submerged. It can carry 21 anti-ship/anti-submarine torpedoes or 28 mines.
Defense Minister Kim Tae-young said earlier that he didn't believe the Romeo-class sub was the culprit of the March 26 ship sinking, citing the ship's slow speed and the shallow water in the West Sea.
Most experts have suspected that Sang-O class subs could be blamed for the incident that has left 38 South Korean crewmen dead and eight others missing.
The 34-meter long, 3.8-meter wide Sang-O class is equipped with four Russian 53-65KE (533mm) torpedoes and is also capable of mine-laying. The sub with a crew capacity of five to 10 is known to be mainly used by special forces in infiltrating areas or laying mines.
It is believed to be capable of conducting underwater operations for up to 20 days without refueling. The sub has a speed of 8.8 knots. North Korea's Navy is believed to have built 17 to 22 Sang-O class submarines in the 1990s.
A Sang-O class sub was found stranded off the waters of Gangneung in the eastern Gangwon Province in 1996.
Rep. Kim Hak-song, chairman of the National Assembly's Defense Committee, claimed earlier this month that South Korean intelligence had detected that Sang-O class submarines were active around the time when the Cheonan sank on the night of March 26 after an unexplained explosion.
Kim revealed that Sang-O class submarines stationed at a naval base in Bipagot, just north of the Northern Limit Line (NLL), had maneuvered between March 23 and 27, and one of the subs had disappeared from surveillance systems.
The 20-meter-long Yugo class is comprised of four midget submarines used primarily for infiltration and espionage by North Korea. The class is so named because it was built from plans supplied to North Korea by Yugoslavia in 1965.
It has a submerged displacement of 90 tons and has a speed of 10 knots surfaced and 4 knots submerged. The sub has a capacity of four to six people and two 406 mm torpedoes.
A Yugo submarine was detected and captured off the waters of Ganghwa Island on Nov. 20, 1998, while it was attempting to infiltrate spies, who subsequently escaped back to the North.
North Korea is believed to have 30 Yugo class submarines.
South Korean authorities say the possibility of a semi-submersible's involvement in the Cheonan sinking remains low given the high seas and waves in the West Sea. A mini-submarine does not have the capability to carry torpedoes that could have destroyed the 1,200-ton Cheonan, they say.
North Korea has 5 to 11 five-ton mini-submarines armed with two 320mm torpedoes. They can carry seven to eight people.
A chief investigator into the ship sinking has ruled out the possibility of an onboard explosion and a reef.
``In an initial examination of the Cheonan's stern, South Korean and U.S. investigators found no traces showing that the hull had been hit directly by a torpedo," Yoon Duk-yong, co-chairman of a 130-strong civilian-military joint investigation team, said in a press conference last Friday. ``Instead, we've found traces proving that a powerful explosion caused possibly by a torpedo had occurred underwater. The explosion might have created a bubble jet that eventually generated an enormous shock wave and caused the ship to break in two."
There has been lots of speculation over what caused the ship to sink near the sea border with North Korea - reasons range from an accident to a deliberate attack.
Yoon's remarks bolstered suspicions of a torpedo from a North Korean submarine or an explosion by a mine placed either by the South or North Korea. Earlier, Cheong Wa Dae and defense authorities downplayed North Korea's involvement, in order not to provoke the communist state at a time when multinational talks on its nuclear weapons program were set to resume after a year-long hiatus.
Speculation has persisted that North Korea may have caused the incident as it occurred near the NLL, the de facto sea border that the North has never recognized.
Naval skirmishes between the two Koreas occurred in 1999, 2002 and last November near the NLL.