The two Koreas have ramped up their rhetoric against each other, with South Korea's president pledging unsparing retaliation if attacked again and a top North Korean official threatening a "sacred" nuclear war if provoked.
South Korean troops, tanks and fighter jets put on a thundering display of force on Thursday as President Lee Myung-bak visited with soldiers at a base near the border, while North Korea's elite marked a key military anniversary by lashing out at the South for encouraging war.
For both countries, the rallying cries and military manoeuvres mainly seem designed to build support at home - but they have raised fears of a new all-out war on the peninsula.
The two Koreas and their allies called a truce in 1953 to end three years of devastating war, but violence has flared up from time to time, most recently in the disputed waters off their west coast.
North Korea does not recognise the maritime line drawn by UN forces, and the territorial dispute in the Yellow Sea has erupted into deadly naval skirmishes.
In March, a South Korean warship went down in the western waters, killing 46 sailors. And a month ago, South Korean live-fire drills in nearby waters triggered a North Korean artillery shower on Yeonpyeong Island that killed four South Koreans - the first attack on a civilian area since the Korean War.
Caught by surprise, Seoul has since beefed up its rules of engagement and has staged military drills, including joint exercises with US troops, meant to remind the North of its superior fire power. The South even carried out provocative artillery drills from Yeonpyeong Island on Monday in a bold dare to the North to retaliate.
On Wednesday, rifle-toting marines ringed a hillside near the border where a Christian group lit a steel tower dressed up as a twinkling Christmas tree - a structure easily visible from atheist North Korea.
While meeting troops manning a front-line army base, South Korean president Lee Myung-bak vowed to retaliate if attacked again. "I had thought that we could safeguard peace if we had patience, but that wasn't the case," he told the troops, according to his office. Any surprise attack will be met with an "unsparing" response, he warned.
After days of showing restraint, North Korea condemned the drills as a "grave military provocation". Defence chief Kim Yong Chun said North Korea is prepared to launch a "sacred war" and poised to use its nuclear capabilities to defend itself.