Alleged NKorean attack on sub came near US-South Korea anti-sub maneuvers

[June 05, 2010]  WASHINGTON (AP) -- The night a torpedo-armed North Korean submarine allegedly sank a South Korean patrol ship, the U.S. and South Korea were engaged in joint anti-submarine warfare exercises just 75 miles away, military officials told The Associated Press.

The blast that sank the Cheonan, the worst South Korean military disaster since the 1950-53 Korean War, showed how impoverished nations such as North Korea can still inflict heavy casualties on far better equipped and trained forces, even those backed by the might of the U.S. military.

Defense Secretary Robert Gates said Friday that plans for more joint U.S.-South Korea anti-submarine exercises, announced after the sinking of the Cheonan, are on hold awaiting United Nations action on the incident.

In part, Gates said, there is concern about instigating another rash act by the North Koreans.

Two months after the sinking, U.S. officials for the first time disclosed details of the joint naval exercise held the same day as the attack on the Cheonan. Forty-six South Korean sailors died on the warship, which was not involved in the exercise but on routine patrol near disputed waters.

Military officials said the drill could not have detected Pyongyang's sub. Officials and defense experts said that a minisub would have been difficult for even a nearby ship to track in shallow coastal waters.

"A small submarine in shallow waters is very hard to detect," said John Pike, director of GlobalSecurity.com, a military think tank.

What surprised experts was that a 130-ton minisub could without warning take down a warship nine or 10 times its size, a power mismatch called asymmetric warfare.

"To us, stealth denotes the latest technology - billions of dollars in research and development in armaments," said John Park, a Korea expert at the U.S. Institute of Peace. "The North Korean version of stealth is old-school diesel-battery operated subs that evade modern detection methods."

An South Korean-led investigation into the sinking concluded last month that the evidence overwhelmingly pointed to the North, but Pyongyang has steadfastly denied any involvement.

South Korea and its allies, meanwhile, have called the attack a shocking provocation, even for the regime of North Korea's eccentric Communist dictator Kim Jong Il.

Western experts say there are still questions about exactly what happened that night off Baengnyeong island.

One U.S. official privately said the sinking may not have been an intentional attack at all, but the act of a rogue commander, an accident or an exercise gone wrong. He spoke on condition of anonymity because he was not authorized to discuss the incident publicly.

That would be for North Korea to explain, said the official, but so far Pyongyang's only response has been denial and indignation. A statement run by state media threatened war in response to any attempt to punish the North.

"Because of the South Korean war-loving, mad puppets and American invaders, the North and South relationship is being driven to a catastrophe," Choi Yong Rim, a high-ranking North Korean Party official, told a Pyongyang rally last week.

U.S. and South Korean forces can easily monitor the movements of North Korean submarines when they operate on the surface.

Underwater, tracking submarines relies on active or passive sonar. Passive sonar uses microphones to listen for the sounds of sub operations. Active sonar emits sounds and listens for the echoes as they bounce off of submerged objects.

The Cheonan was operating its active sonar at the time, South Korea's Navy officer Kim Young-kyu, a spokesman for the U.N. Command in Korea, told The Associated Press. It wasn't clear why the ship didn't detect the sub.

After the blast, a South Korean commander dispatched a patrol boat to look for subs.

But officials said the vessel couldn't locate any, perhaps because of the weather, currents and rough conditions that chilly March night. Those factors, as well as the rocks and ledges in shallow water, can all affect the reliability of sonar, experts say.

Sonar technology has traditionally been designed to operate in deep waters and used for convoy protection rather than coastal defense.

"There's a lot of equipment that works pretty well against big submarines out in the deep ocean, but doesn't work so well against small submarines in shallow water," analyst Pike said. "We've got the same concern with Iran and the Persian Gulf."

North Korea is believed to have a fleet of 70 submarines, including some 50 that are small but still capable of carrying a torpedo.

The night before the Cheonan sank, two U.S. destroyers and other ships maneuvered and practiced tracking while a South Korean navy submarine played the role of target.

The U.S.-South Korean anti-sub exercise began at 10 p.m. March 25 and ended at 9 p.m. the next day, Army Col. Jane Crichton, a spokeswoman for U.S. forces in Korea, told The Associated Press. The exercise was terminated because of the blast aboard the Cheonan.

The submarine drill was part of annual U.S.-Korea war games called Key Resolve/Foal Eagle, which are intended to keep forces ready in the event another major war erupts on the Korean Peninsula.

Key Resolve was an 11-day computer simulation started early in the month. Foal Eagle followed at midmonth and included live firing by U.S. Marines, aerial attack drills, urban combat and other training as well as the anti-submarine warfare drill.

As the exercises got under way, Army Gen. Walter Sharp, commander of U.S. forces in Korea, said it was practice for "all the threats that North Korea can throw at us."

North Korea claimed the exercises amounted to attack preparations and demanded they be canceled.

The North's military said that it would bolster its nuclear capability and break off dialogue with the U.S. in response to the drills. But Pyongyang rails at Key Resolve/Foal Eagle every year, one U.S. official said.

Seoul has taken the sinking of the Cheonan as a wake-up call, and vowed to review and strengthen its defenses. The U.S. is planning two major naval exercises with South Korea in the coming weeks on top of the more than dozen of various types that it holds each year.

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Associated Press writers Jean H. Lee and Kwang-Tae Kim in Seoul contributed to this report.

[Associated Press; By PAULINE JELINEK]

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