South Korean patrol boats and corvettes are able to detect a mere 30 percent of submarines at a time when North Korea is increasing the frequency of submarine infiltration drills.
According to data the Joint Chiefs of Staff and the Defense Intelligence Agency submitted to Democratic Party lawmaker Shin Hak-yong of the National Assembly's Defense Committee, North Korean submarine infiltration drills in the West Sea increased to 28 between January and August 2010, from a mere two in the same period in 2008 and only five in 2009.
In the same period this year, North Korea raised the number of infiltration drills to 50.
Infiltration exercises using semi-submersible craft also rose from 14 in the first eight months last year to 22 this year. The number of submarine exercises in the East Sea soared from 25 in the January-August period last year to 39 this year.
This year's submarine exercises in the West Sea were reportedly concentrated between June and August. "There's a likelihood that the North will seek a chance for provocation as a lot of North Korean and Chinese fishing boats are busy in the West Sea during the blue crab harvest season" that began in early September, Shin said.
But South Korean patrol boats and corvettes tasked with defending the coasts lack the capacity to detect subs. Some navy patrol boats including the one plying waters near Baeknyeong Island when the Navy corvette Cheonan was attacked in March last year failed to spot any enemy subs at all during an anti-sub exercise in August the same year.
Corvettes of the Second Navy Fleet detected a mere 28 percent of the submarines taking part in exercises in the first quarter last year.
"The military needs to step up vigilance around the northwesternmost islands until the blue crab season comes to an end," Shin said. "It needs extra surveillance equipment, including up-to-date destroyers that have excellent submarine detection capabilities."