South Korea's president has compared a deadly North Korean artillery barrage to the September 11 terrorist attacks on the United States, saying the South must strengthen defences and cannot let the North "covet even an inch of our territory".
Lee Myung-bak, speaking to the country in a New Year's speech, said the November 23 shelling of Yeonpyeong Island was a transformational event for South Korea.
He vowed to hit back hard if attacked again, but he also opened the door for possible peace talks, saying South Korea has "both the will and the plan to drastically enhance economic cooperation" should the North show it is willing to fulfil past nuclear disarmament commitments.
However, the overwhelming focus of his speech was a tough promise to improve South Korea's defences.
"The situation before and after the provocation against Yeonpyeong Island cannot be the same," Mr Lee said. "Any provocation that would pose a threat to our lives and property will not be tolerated. Such provocations will be met with stern, strong responses."
Mr Lee was severely criticised for responding too slowly and too weakly to the shelling near the Koreas' disputed western sea border - the North's first attack on a civilian area since the 1950-53 Korean War.
His government has responded by replacing the defence chief, strengthening security and pushing to deploy additional troops and weaponry to Yeonpyeong, which lies just seven miles from North Korean shores.
After the September 11 terrorist attacks, the United States "went back to the drawing board to devise new security and national strategies, because the safety and security of its people had come under threat," Mr Lee said. "The shelling of Yeonpyeong Island also served as an opportunity for us to reflect on our security readiness and overhaul our defence posture," he said. "There cannot be any delay in establishing security measures."
Despite his strong words, Mr Lee also said peace between the two Koreas is still possible. "The door for dialogue is still open," he said.
The North shelled Yeonpyeong Island, killing two civilians and two marines, after warning the South not to conduct live-fire drills there. North Korea claims the waters around Yeonpyeong as its own territory, refusing to recognise the maritime boundary drawn in 1953 by the United Nations without consulting with the North.