The president, who renounced his liberal predecessors' engagement policy toward Seoul's former wartime rival, agreed. Holding military exercises for national defense is a "natural thing" for a sovereign country locked in a military standoff, Lee said in thinly veiled support of the conservative response.

The public, anxious of escalating tension yet irate about Pyongyang's series of provocations, also sided more with the ruling camp. According to a survey released Tuesday by polling agency RealMeter, 66.6 percent of the respondents supported the live-fire drill. Only 26.2 percent said it should stop.

Military tension in South Korea never really helped liberal agendas. The engagement policy by former Presidents Kim Dae-jung and Roh Moo-hyun, commonly dubbed the "sunshine policy," did have its glorious days when the two estranged neighbors got chummier.

Those days are over, says the government. The ruling camp branded the sunshine policy an "utter failure," with Lee declaring in his recent national speech that South Korea no longer expects the DPRK to "abandon its nuclear program or its policy of brinkmanship on its own."

Still, the opposition would not blink.

"Simply put, it was reckless to go ahead with the firing drill, " Sohn Hak-kyu, chairman of the Democratic Party, said Tuesday in a meeting with senior party members, saying the world now sees the Korean peninsula as a disputed area. It was not a routine drill as the government claims but a military operation, he said.

"Our opposition to the drill lies in the belief that people's lives should be what's the most important," the opposition leader said, cautioning against escalation of the conflict and constant fear of war.

Opposition lawmakers also question if the current heavy-handed dealings with the DPRK stem from political calculations. National defense has always been a self-proclaimed forte of the conservative government and helped it woo voters in key elections.

The president would have "accelerated his political dictatorship" if the DPRK militarily responded to the firing exercise, Sohn said. The drill seemed aimed at directing the domestic political situation in favor of the government for political gains, the left-leaning Democratic Liberal Party also said.

The ruling bloc, clearly annoyed, retorted in a pointed question Tuesday. "Why is the opposition so tolerant of North Korea while saying no to every single thing the government does?"