North Korea has denied holding any South Koreans against their will. The missing soldiers were eventually counted among the war dead and largely forgotten in the South. Mr. Han’s mother died in 1961 believing that her son had been killed in battle. (His father died before the war.)
Then, in 1994, an emaciated refugee from North Korea named Cho Chang-ho was found adrift on a ramshackle wooden boat off South Korea. He turned out to be a South Korean lieutenant who had survived prison camps and coal mines in the North. In the South, he was found to have black lung disease.
More aging P.O.W.s fled to the South in the following years, as a famine forced the North to ease control on its people. They all testified in government debriefings, memoirs, news conferences and interviews to forced labor, starvation and deaths in North Korean mines and identified hundreds of fellow war prisoners still alive in the North. Shocked that their long-lost sons and siblings were still alive, South Korean families wanted to help them flee the North. Soon, a cottage industry developed for human traffickers to smuggle refugees out.
So far, 80 P.O.W.s have made it to South Korea, some later testifying in court in support of Mr. Han’s case — the seeds of which were planted by South Korean activists, who suggested the lawsuit in 2016.
Mr. Han, who retired from the Hamyon coal mines at age 60, was living in Kyongwon, in northeast North Korea, when a man showed up in August 2001, asking whether he wanted to meet his South Korean relatives. Mr. Han said he followed the man across the river border to China, his youngest son tagging along.
Around that time, Han Jae-eun, Mr. Han’s youngest brother in South Korea, got a call from a human trafficker.
“I first could not tell whether the man was telling the truth or it was a scam,” said his brother, a taxi driver in Incheon, west of Seoul. “The brother we all thought was dead more than a half century ago turned up alive.”