Seoul decided to revive the military operation concept of seeing North Korea as its “main enemy“ after a team of investigators found that the North torpedoed its warship in March.

"Reviving the ‘main enemy’ concept will be considered at the working-level,“ presidential spokesperson Kim Eun-hye said.

"Our military failed to clarify the ‘main enemy’ concept,“ President Lee Myung-bak was quoted as saying by Kim at a meeting with senior nongovernmental advisors on Tuesday.

"(The South Korean military) neglected the threats close by and focused on potential threats outside the Korean Peninsula.“

Another presidential aide said on condition of anonymity that it was ”natural“ for Seoul to revive the main enemy concept, which was deleted from defense policy papers six years ago.

“The government has begun working-level discussions to go back to seeing North Korea as the main enemy,” he said.

"What now remains is the technical issue of how to phrase the concept and in which parts of the defense white paper."

North Korea first started to be referred to as the “main enemy” in South Korean defense white papers in 1995 under former president Kim Young-sam, a year after a North Korean general threatened to turn Seoul into a “sea of fire.” But since 2004, the description was replaced by “direct military threat” or other watered-down expressions.

The government’s decision to reuse the “main enemy” concept comes as Seoul views the Cheonan’s sinking as the North’s “clear military provocation” and vowed to “maintain the principle of proactive deterrence” by immediately exercising its “right of self-defense” against future provocations by the North.

Lee has said earlier that "a lack of a clear adversary in terms of national security" may have led to "internal confusion within the military," giving weight to voices within his office that they should return to seeing North Korea as the official adversary.

“From now on, the Republic of Korea will not tolerate any provocative act by the North and will maintain the principle of proactive deterrence,” Lee said in a televised address to the nation on Monday.

“If our territorial waters, airspace or territory are militarily violated, we will immediately exercise our right of self-defense.”

The main enemy concept has been a source of an ideological dispute here as views of national security greatly vary among the Korean population 60 years after the Korean War, started by the North’s invasion, tore the peninsula in two.

The Koreas, divided by a heavily guarded border, are technically still at war, as the 1950-53 Korean War ended in a truce instead of a peace treaty.

Some have argued that military discipline has grown lax without any particular subject set for the military to fight against while others said that reviving the term would only cause inter-Korean ties to deteriorate.

Until recently, the Defense Ministry has remained cautious about reusing the term, saying it is seeking to strengthen troop education to underscore continuing military threats from the communist state.

“Most foreign countries don’t use the expression, the ‘main enemy.’ What is important is that thinking of anything that poses a threat to our citizens and our territory as our enemy, the military should make all preparations for it,” Defense Minister Kim Tae-young told a parliamentary committee on April 30.

The return of the “main enemy” may not be simply a change of moniker as President Lee hinted about a major paradigm shift in Seoul’s North Korea policy.

Lee started his address on Monday by saying that the “Korean Peninsula is facing a critical turning point,” possibly referring to his shift from the 10 years of Sunshine Policy and the growing instability in North Korea.

South Korea plans to hold antisubmarine drills in the West Sea on Thursday ahead of joint exercises with the U.S.

South Korean Navy chief Kim Sung-chan met with U.S. Naval Forces Korea commander Pete Gumataotao on Monday to discuss ways to strengthen cooperation as part of Seoul’s countermeasures against North Korea.

South Korea and the U.S. agreed to closely work together for the joint antisubmarine drill between June and July, and the naval blockade exercise under the U.S.-led Proliferation Security Initiative, a global antiproliferation program.

By Kim So-hyun  (sophie@heraldcorp.com)