By Park Chan-Kyong
SEOUL, South Korea - When North Korea sent a rain of deadly shells across its border this week, the South retaliated not just with artillery but also a weapon that the hardline regime truly fears - balloons.
According to media reports, Seoul quickly launched a propaganda offensive meant to undermine the iron-fisted rule of Kim Jong-Il by sending anti-Pyongyang leaflets on balloons across the heavily fortified border.
"We've released the balloons carrying leaflets as retaliation against the shelling," a military official was quoted as telling the Joongang Ilbo daily.
"The leaflets contain criticism against Kim Jong-Il and the third-generation hereditary succession," the unnamed official said in reference to the North's expected looming power transfer to Kim's 27-year-old son Jong-Un.
Seoul had promised Pyongyang six years ago to halt such psy-ops, or psychological operations, but the South reportedly resumed them after the North stunned it Tuesday by shelling an island and killing four people.
Some 400,000 leaflets denouncing the North's sanctified leadership were floated across the Demilitarised Zone (DMZ) just hours after the North launched a barrage of shells on Yeonpyeong island, the reports said.
The leaflets had reportedly been prepared following the sinking of a South Korean warship in March, with the loss of 46 lives, which Seoul and an expert panel have blamed on a North Korean submarine torpedo attack.
Military officials, who declined to comment on the report, have reassembled another powerful weapon in the war of ideas for the first time in years - a massive, high-voltage array of army-green loudspeakers.
The speakers are designed to blast anti-regime and pro-democracy messages deep into North Korea's border region - as far as 24 kilometres (15 miles) at night and 10 kilometres during the day.
So far they have stayed silent, but South Korea's defence ministry has warned that the speakers will be switched on in response to any fresh cross-border provocation.
North Korea, one of the most closed societies on earth, has in the past threatened to open fire on the speakers if they are activated, and on locations from where propaganda balloons are released.
The two Koreas are technically still at war, as their 1950-1953 conflict ended in a truce, not a peace treaty.
When defectors and activists launch balloons with leaflets and consumer goods, North Korean troops are believed to use them for target practice, wrote Peter Beck, a long-time expert on North Korea, in a recent paper.
One activist-balloonist, Beck wrote, was considering sending copies of George Orwell's Animal Farm and DVDs with a combination of evening news broadcasts and popular movies from South Korea.
The fact that Pyongyang has reacted so furiously to the leaflets in the past suggest that they are effective in rattling the communist regime, another military official was quoted as saying by the Joognang.
"I think the leaflets are even more powerful than artillery shells."