JINDONG, South Korea — The ginseng field owned by Yun Ok-hwa lies just a minute’s walk from the demilitarized zone that divides South and North Korea. As a cuckoo sang in a nearby acacia grove recently, its melodic call was punctuated by a more ominous sound, the pounding of South Korean artillery.

And if South and North Korea follow through on their threats in the wake of the sinking of a South Korean warship in March, Yun will soon hear other sounds: high-powered South Korean loudspeakers blaring propaganda across the border and North Korean guns blasting at the speakers. “I’m afraid things are going back to the old days,” Yun, 58, said. “It takes six years to grow and harvest ginseng. Here I have roots that are two, three, four, six years old — a big investment. If something happens with North Korea, I’ll lose everything.”

An estimated 20,000 South Koreans like Yun are carving out a living just below the demilitarized zone under special military permits that allow them to cultivate an area that is off limits to other civilians and that is guarded by soldiers and minefields.

Their anxiety over the threat to their livelihoods echoes that of South Koreans in general at living in one the world’s most prosperous countries, next to one of the world’s poorest and most isolated. They express a peculiar mix of bitterness and resignation at the bonds of geography and kinship they share with their northern neighbors.

“They are a brainwashed people, a nation of desperadoes, an army of suicide bombers,” Yun said. Gazing over the black plastic sheeting covering her ginseng she added, “If war breaks out, we have far more to lose than the North Koreans do.”

Over the decades, South Korea’s response to the North’s provocations has shifted from calls for retaliation (“The best medicine for a rabid dog is a club” was a slogan popular in the 1970s) to the more recent “sunshine policy” of pouring aid into the North to encourage it to shed its hostility. Neither approach worked as the South had hoped.

Now, President Lee Myung-bak of South Korea has seized on the sinking of the ship, the 1,200-ton Cheonan, and the death of 46 sailors, to focus his tougher, dual approach of putting unilateral and international pressure on the North. He has severed most trade and contacts with the North and vowed to resume the propaganda broadcasts.

Until 2004, when both North and South silenced their loudspeakers, such broadcasts were part of daily life for farmers and soldiers around this border town north of Seoul.

Each morning, a sweet-voiced North Korean woman greeted the South Koreans and exhorted them throughout the day to defect to the “socialist paradise.” From the other side, a South Korean woman updated North Korean soldiers on the collapse of the Soviet bloc and asked: “Have you filled your empty stomach today? Come to the South, a land of prosperity and freedom!”

In the new confrontation with the North, Lee’s aides say that the president thinks that time is on his side and that he needs to keep the pressure on. The North’s economy is a shambles. The North Korean leader, Kim Jong Il, is ill, and the leadership abilities of his third son and reported heir, Kim Jong Un, 27, are untested.

But Kim’s government survived a famine in the mid-1990s with its grip on power intact. China continues to funnel emergency aid to help bolster North Korea, which sees U.N. sanctions as proof of foreign hostility and a justification for its continued development of nuclear weapons.

“There is a sense of resignation when South Koreans sigh at North Korean provocations, saying, ‘There they go again,”’ said Chang Yong Seok, a North Korea expert at Sungkonghoe University in Seoul, the South’s capital. “They appear indifferent because they know that neither side can risk a war. To them, North Korea is like a desperate gangster wielding a knife who has to be bought off with some cash.” Chang says that Lee’s tough talk — he says the president is seeking an “implosion” of the North Korean government — does serve to provide an “ideological catharsis” for his conservative base. But it could eventually fail, Chang said, because such outside pressure deepens North Koreans’ hostility toward the South and strengthens their solidarity with Kim’s government.

This political conundrum has spawned a bizarre coexistence of peace and tension along the Korean demilitarized zone, itself a misnomer because, 57 years after the Korean War ended with a truce but no peace treaty, this remains the world’s most heavily armed border.

Yun and her husband, Lee Gwang-nam, 86, had to clear 400 land mines to cultivate her ginseng field. In the nearby village of Jangpa-ri, a community of 500 households, more than a dozen people have been killed or maimed over the years by stepping on mines or mishandling stray bombs. Among them was Lee’s second son, who lost an arm and a leg.

A neighbor, Woo Jae Ok, an 85-year-old rice farmer, said he was disappointed that Lee had not ordered some sort of military retaliation for the sinking of the Cheonan. Woo, who fled the North during the 1951-53 war, left behind his family, including a 4-year-old daughter he never saw again. For him, the war has not ended.

“We should smash the North Korean regime to liberate its people,” he said. “I’m losing any hope of ever returning home.”

If Woo is consumed with hatred of the North Korean government, his son, Woo Kyong-bok, who was born in the South two years after the war ended, directs much of his anger at the U.S. military, which operates gunnery ranges near Jangpa-ri. Until American officials agreed on a detour in 2003, their tanks routinely rumbled through the village, “shaking our floor at 4 a.m. and causing our cows to miscarry,” the son said.

Now, his complaint is a drop in land values.

When South Korea pursued its so-called sunshine policy, word spread that the Koreas would build a joint industrial park near the village, like the one they built in Kaesong, a North Korean border town. Real estate agents rushed up from Seoul. Property prices more than doubled.

“Now,” the younger Woo said, “there’s no more interest in the land here.”