On the night of March 26 last year, a 1,200-ton South Korean Navy patrol ship, Cheonan, sank just south of the tense Yellow Sea border with North Korea, killing 46 of its 104 sailors.
The cause of the South Korean Navy's nightmarish experience, which severely stunned and saddened people across the world, had initially remained a mystery, though the majority of South Korean people instantly pointed at North Korea as the prime suspect.
Two months after the sinking of the Cheonan, the results of an international investigation found a North Korean midget submarine responsible for deliberately torpedoing the 1,200-ton corvette, claiming 46 lives. They were on a routine patrol mission.
The North's attack, one of the worst disasters for the South's military since the end of the 1950-53 Korean War, caught commanders here off guard and revealed that their better equipped forces had been vulnerable to an unconventional, or "asymmetrical," attack by Pyongyang.
"We judged that the torpedo attack on the Cheonan warship was the beginning of North Korea's asymmetrical aggression," said a senior commander at the Joint Chiefs of Staff.
"The military has taken the Cheonan attack as a wake-up call and we have learned a lot from the tragedy about weapons arsenal, combat preparedness and security awareness among all ranks of soldiers," the commander said on the condition of anonymity.
The wreckage of the Cheonan is on display at the 2nd Fleet Command in Pyeongtaek, south of Seoul. (Yonhap file photo)
A measured martial mood among military brass in South Korea was further spreading after North Korea rained down artillery shells on Yeonpyeong Island, about 12 kilometers off the North's coast, in the Yellow Sea last November. Two marines and two civilians were killed in what was the first attack on South Korean land by the North since the war six decades ago.
In response to increasing North Korean hostilities, South Korean Defense Minister Kim Kwan-jin unveiled a 73-point military reform measure early this month.
The measures call for an early introduction of spy drones and stealth fighters, drastically strengthening fire power and making the command structure of the 650,000-member military slimmer but more efficient.
Among others, South Korea will purchase high-altitude spy drones and stealth fighter jets and deploy them earlier than an initial deployment year of 2015 to strengthen deterrence against North Korea, Kim said.
"The aim is to proactively deter current threats posed by the enemy rather than cope with potential threats in the future," Kim told reporters.
While inspecting soldiers at a front-line unit defending the Yellow Sea islands this month, the outspoken Kim issued an order: "Don't ask whether to shoot or not. Shoot first and report later."
An Inter-Korean engagement policy, U.N.-led sanctions and verbal condemnation have failed to prevent the unruly regime in Pyongyang from provoking Seoul since the war ended with a fragile armistice. Last year's two bold military attacks added deep scars on the complicated relations between the two Koreas.
Many analysts and military officials have suggested that the two attacks last year were in part linked to a move by the North's military to try to establish credentials for its successor-in-waiting, Kim Jong-un. His 69-year-old father, Kim Jong-il, suffered a stroke in 2008 and the son is believed to be in his late 20s.
And the North could launch other forms of aggression this year if its demand to resume the stalled aid-for-disarmament talks on its nuclear program is ignored, analysts said.
"Currently, North Korea seems to have two control towers -- Kim Jong-il and Kim Jong-un -- in the process of succession," said Baek Seung-joo, a senior analyst at the state-run Korea Institute of Defense Analyses. "So, there is a split between hawkish and dovish policies."
"Military aggression and dialogue offensive to the international community should be viewed as tactics to build credentials for Kim Jong-un," Baek said. "I think provocations could continue this year."
Six-party talks involving the two Koreas, the U.S., China, Japan and Russia have been at a standstill since the North walked out in April 2009 and staged its second nuclear test a month later.
Adding to the concerns about the North's nuclear ambition, Pyongyang revealed new, sophisticated uranium enrichment facilities at its nuclear site last November.
Pyongyang claims the uranium enrichment program is for peaceful energy development, but outside experts believe it could give the country a new source of fission material to make atomic bombs in addition to its known plutonium-based program.
Still, chances of restarting the six-party talks are slim as Seoul, Washington and Tokyo oppose holding dialogue with Pyongyang unless the North first takes concrete steps demonstrating its denuclearization commitment, citing the regime's habitual policy of abandoning deals it agreed to while walking away from the talks.
Also, South Korean officials have been wary of the North's sincerity after the first inter-Korean military talks since the Yeonpyeong attack fell through last month, dealing a setback to efforts to ease tensions on the Korean Peninsula.
There is no easy solution when dealing with North Korea as Pyongyang is ready to play a game of "chicken" with Seoul and Washington.
"Even if dialogue restarts in the form of six-party talks, there won't be a breakthrough on nuclear disarmament of the North," said Jeong Young-shik, a senior researcher at the Samsung Economic Research Institute.
"This is because the North won't change its position that uranium enrichment is a peaceful activity," Jeong said.
However, some experts on North Korea in Seoul called for their government to "become flexible" to make the North change its attitude.
"Rather than only requesting that North Korea show its sincerity, we need a strategy and tactic to persuade and lead the North," said Korea University professor Yoo Ho-yeol.
As the first anniversary of the Cheonan attack approaches on Saturday, the Navy invited last week a group of defense journalists for an interview with some of the 58 surviving sailors. They were rescued soon after the sinking.
A year later, they still vividly recounted their desperate struggles to escape the ship and felt a sense of guilt about the 46 sailors who went down.
S. Cpo. Kim Soo-gil, who briefly shed tears, said he remembered the night the Cheonan sank "like it was yesterday."
"Although one year has passed, memories of my colleagues always bring me to tears," said 37-year-old Kim, who was transferred to ground duty after showing symptoms of post-traumatic stress disorder.
Lt. Park Yeon-soo, 28, said, "The biggest hardship for us is a sense of guilt that we failed to share our fate with our 46 comrades. But we are trying to deal with our hurt over the loss of their lives."
Of the 58 survivors, five showed symptoms of post-traumatic stress disorder and another 19 were categorized as at high risk of suffering from it as of October last year, according to data from the defense ministry.
Lt. Park Yeon-soo (R) and S. Cpo. Kim Soo-gil speak to journalists at the 2nd Fleet Command on March 18. (Yonhap)