ON A RESTLESS night in April 1970, Lee Jae-geun, one of 27 South Korean fishermen aboard a trawler in the Yellow Sea, awoke from a nightmare. He had dreamt that Korea was struck by three titanic waves, each stronger than the last. The final wave swept aside mountains, deluged the country and left the land divided. It was, he thought, a bad omen. And so it proved. A few nights later a North Korean patrol intercepted his trawler about 50 miles south of the Northern Limit Line, a disputed maritime border between the two Koreas. Armed patrolmen boarded the trawler and abducted its crew. Most of them were repatriated later that year, but the North Koreans had grander designs for Mr Lee, hoping to train him as a spy. It was three decades before he escaped.

The division between north and south remains Korea’s enduring tragedy. It was imposed in 1945 by the Allied powers that liberated the country from 35 years of cruel Japanese rule. In 1950 it was almost erased by a wave of North Korean troops that swept down the peninsula under the command of Kim Il Sung, a Soviet-backed ruler who outlasted the Soviet Union itself. Another wave of troops, mostly American but fighting under the United Nations banner, then reversed the North Korean tide. Eventually the UN forces succumbed to a third wave of Chinese troops which drove them back to the 38th parallel, a latitudinal reference line that still divides the two Koreas. Everybody ended up roughly where they had started.

On land the dividing line is painstakingly demarcated and heavily fortified. But at sea the border is both physically and legally indistinct, dogged by disputes, incursions and abductions. The South Korean government knows of over 500 of its citizens abducted since 1955 who are still missing.

Mr Lee is no longer one of them, but the country to which he escaped is not the one he left behind decades ago. Its economy, politics and culture have all changed beyond recognition. As a teenager Mr Lee had served as an errand boy for Seoul’s police and knew every nook and cranny of the city. But in the vast metropolis he returned to 30 years later, he “couldn’t tell left from right”, he says.

When he was abducted, South Korea’s income per person was about $2,000 a year (at purchasing-power parity), roughly equal to North Korea’s at the time. As a fisherman, Mr Lee counted as comfortably middle-class. By the time he returned in 2000, South Korea’s income per person had grown almost tenfold (see chart). In 2010 the country became one of only 15 in the world with a GDP of over $1 trillion.

Two years after Mr Lee’s capture, Hyundai began work on a shipyard in Ulsan, Mr Lee’s southern home town. The yard is now the biggest in the world. Its red Goliath cranes hoist walls of steel measuring 20m by 40m in nine dry docks, making vast container ships and sophisticated drilling vessels for customers from 48 countries. Internationally competitive industries like these have helped make South Korea the world’s seventh-biggest exporter of goods.

And not only goods. Instead of the waves that haunted Mr Lee’s dreams, a Korean wave of films, music and soap operas has inundated Asia and begun to spread beyond. South Korea, so long subject to foreign influence, is now influencing others. One of its diplomats heads the United Nations. Lady Gaga wears its fashions. The South Korean rapper Psy created the most-watched YouTube clip ever. Even in Pyongyang, North Korea’s capital, South Korean music and drama circulates widely, if furtively, on memory sticks and DVDs. Youngsters are wearing their hair styled like their Southern cousins.

Back in 1970 South Korea was ruled by Park Chung-hee, whose daughter, Park Geun-hye, now holds the presidency. But in the intervening years the polity she heads has travelled almost as far as the economy. Her father came to power in a coup in 1961, then in 1972 dissolved the National Assembly and introduced a newly authoritarian constitution. His daughter, by contrast, won the presidency last December in a free and fair election, South Korea’s sixth since 1987. She racked up the highest share of the vote since her father’s victory in 1971.

Poignant reminder

If South Koreans want to remind themselves of the progress they have enjoyed, they need only look north, where men on average measure up to 8cm less and die 12 years sooner. North Korea’s Kim dynasty is now in its third generation, with power passing in 2011 to Kim Jong Un, who may not yet be 30 (no one is quite sure) but models his gestures and embraces on those of his grandfather, Kim Il Sung. The country’s output of cereals, which collapsed in the mid-1990s, has only just regained the level it reached in 1982. A visiting NGO hoping to improve yields on a collective farm had to dust off agricultural techniques that had not been used in the south for decades. To help its electrical equipment cope with the north’s wild swings in current, it had to order a voltage stabiliser not seen in the south since the 1980s.

In escaping to the south, Mr Lee achieved a personal reunification that still eludes his country as a whole. But he did not find it easy. In the north he had been a mechanic, making ships’ engines, but when he looked for similar work in the south he found that it was now done by machines. Still, his predicament is shared by many older South Koreans who have not managed to keep up with a now much more sophisticated economy.

South Korea does not make best use of these older workers, who constitute a growing proportion of the country’s population. It forces many of them to retire prematurely instead of retraining and re-educating them. By contrast, it overeducates its young, who toil away in expensive crammers and devote years to preparing for the university entrance exam. Families compete with each other in an educational arms race that is almost as ruinous as the military competition with the north. Extra qualifications are a ticket to the best jobs, and the best jobs are still concentrated in the government, the banks and the chaebol (the big family-owned conglomerates).

South Korea’s working-age generation faces a triple burden. It must take care of older people, who are growing in number, younger people, who are expensive to educate, and perhaps eventually North Koreans, who will have to be integrated into the economy if the two Koreas are ever reunified. Daunted by these burdens, many South Korean women are delaying childbirth and having fewer children. The country’s fertility rate has fallen further and faster than in almost any other country. Its population, which surpassed 50m last year, is projected to fall below that number again by 2045.

Young South Koreans feel little connection with those on the other side

Many young South Koreans are trying to forget their ties to the north. Their grandfathers and great-grandfathers were preoccupied with the communist enemy, their fear and loathing kept alive by heavy propaganda during the years of dictatorship. The generation born in the 1960s, known as the 386 generation in homage to the Intel 386 microchip, was equally focused on the north, arguing that anti-communist fervour was making reconciliation and reunification impossible. Today’s southern youngsters, by contrast, feel little connection with the people on the other side of the 38th parallel. They are secretly relieved that for now reunification seems only a distant possibility. They do not burn with hatred for the north, nor do they romanticise it, as some older leftists used to do. They simply want to ignore it. But the north does not allow itself to be ignored.