POCHEON, South Korea: North and South Korea beat the drums of war Thursday, with each threatening the other with immediate retaliation if attacked. Seoul has staged days of military drills in a show of force meant to deter North Korea, including live-fire exercises earlier this week on a front-line island shelled by the North last month. Angered by the exercises, North Korea threatened Thursday it would launch a “sacred” nuclear war if Seoul hit it and warned that even the smallest intrusion on its territory would bring a devastating response. The two sides are still technically at war because their 1950-53 conflict ended in a truce not a peace treaty, and a US governor who recently made an unofficial diplomatic mission to the North has said the situation on the peninsula is a “tinderbox” and the worst he had ever seen it. Still, the latest rhetoric seemed likely to be just that, words aimed at stirring pride at home and keeping the rival at bay. Defense chief Kim Yong-chun said North Korea is “fully prepared to launch a sacred war” and would use its nuclear capabilities, calling Monday's drills a “grave military provocation” that indicated South Korea is pushing to invade the North. Kim told a national meeting in Pyongyang that the North's military will deal “more devastating physical blows” to its enemies if they cross into the North's territory even slightly, the official Korean Central News Agency said in a dispatch. While the remarks mentioned South Korea's military drills, it's more telling that they come on the eve of the 19th anniversary of leader Kim Jong-il's appointment as the supreme military commander – a day when Pyongyang will want to rev up patriotic spirit. Earlier in the day, South Korea's president vowed a strong response if North Korea attacks again as his military conducted its largest air-and-ground firing drills of the year at training grounds near the tense Korean border. “I had thought that we could safeguard peace if we had patience, but that wasn't the case,” President Lee Myung-bak said during a visit to a front-line army base near the Koreas' eastern land border, according to his office. “Our military must ... make unsparing response if it suffers surprise attacks.” Near the Koreas' land border, South Korean tanks fired artillery and fighter jets zoomed by to drop bombs Thursday, signaling South Korea's determination to demonstrate and hone its military strength at the risk of further escalation with North Korea. The boom of cannons echoed through the valley, and the hills erupted in smoke at training grounds in mountainous Pocheon about 20 miles from the border. Rockets streamed through the air and slammed into the side of a hill as helicopters overhead fired at targets and F-15 jet fighters dropped bombs. The drills were the armed forces' largest joint firing exercises this year and the biggest-ever wintertime air and ground firing exercises in terms of the number of weapons mobilized and fired, government and army officials said.