SEOUL, South Korea — Renate Kleinle and Hong Ok-geun met in 1955, when they attended the same freshman chemistry class at Friedrich Schiller University in Jena, in East Germany. Hong was an exchange student from North Korea, then East Germany’s communist ally.

They fell in love. Because both governments frowned on marriages between North Korean students and East Germans, the couple married in 1960 in a rural town where the local authorities were unaware of the national government’s policy. No guests attended.

Then, one year later, politics intervened. The North Korean government, apparently worried after some students defected to the West, recalled all 350 North Korean students in East Germany.

Hong was given 48 hours to pack. They both cried as she saw him off at the Jena train station. That was the last time the couple saw each other until this summer, 47 years after they parted.

Renate Hong was allowed to travel to North Korea in late July after long negotiations between the German Foreign Ministry, and the Red Cross and their North Korean counter- parts. Hong Ok-geun is 74 and remarried. Renate Hong is 71 and never married again. Their two sons, who went along on the trip, are now 48 and 47.

The family’s 12-day reunion was extremely unusual. North Korea remains one of the world’s most reclusive countries, and its leader, Kim Jong-il, maintains an iron grip on what the country’s citizens are permitted to learn about the outside world, especially the West. Most North Koreans have no direct mail, international telephone or Internet service.

The government has allowed reunions of some Korean families divided during the Korean War, but they have been rare, and many Koreans died before reconnecting with spouses and children.

After Hong Ok-geun left Germany — leaving their son, Peter, 10 months old, in his wife’s arms; at the time, she was pregnant with their second son, Uwe — he was able to send some letters. His last letter, dated Feb. 26, 1963, asked whether Uwe, the son he had never met, could walk yet. And then he wrote, “This sounds like a real goodbye letter.” After that, the letters stopped, and Renate Hong’s letters were returned as undeliverable. Her appeals to the North Korean Embassy to be reunited with her husband were denied.

She kept a scrapbook that included pages on which she had practiced writing one of the few Korean phrases that she had learned, dasi bopsida — “Let’s meet again.”

After decades spent working as a teacher and researcher and rearing her sons, Renate Hong renewed her efforts to find her husband two years ago when she appealed to the German government, and Red Cross societies in Germany and South Korea. Early last year, the German Red Cross located Hong Ok-geun, a retired government scientist living with his new family in a town on the east coast of North Korea.

With the help of the German government, Renate Hong wrote to him in March 2007. Four months later, on her 70th birthday, his reply arrived with photographs of him at a meeting of scientists wearing several medals on his chest.

“Our international love brought us much pain,” he wrote in German. “I dearly wanted to see you and my sons. I never gave up hopes that if I lived long, one day I would be able to see you again.

“I had wanted you to be my life partner,” he continued. “But politics do stupid things.”

He added that he and other North Koreans were suffering economic hardship because of the policy of the United States of “stifling” North Korea, echoing the country’s Communist Party line.

After two years of negotiations, North Korea agreed to a reunion, influenced perhaps by the establishment of diplomatic relations with the unified Germany in 2001 and German development aid.

Finally, last month, Renate Hong and her sons left for North Korea. She took books, clothes, vitamins and a camera.

When they met, Hong Ok-geun gave her a ring and a blouse. They pored over albums of childhood photographs of their sons. They saw each other every day while she was in Pyongyang, the capital, and spent time together at a mountain resort.

“Because he didn’t have a chance to speak German for 47 years, he first found it difficult to understand me,” Renate Hong said. “But he quickly recovered his language skill. He is an old man now, but I saw no change in his manners and the way he spoke. We had private time just between the two of us.”

Hong Ok-geun had one daughter and two sons with his North Korean wife. The daughter joined the reunion. Hong Ok-geun’s North Korean wife wanted to meet Renate but could not join the reunion because of an illness, Renate Hong was told.

When the couple parted, Hong Ok-geun said he wanted to see her again next year, but it remains unclear whether North Korea will allow a second reunion.

“My husband said he was sorry for leaving everything to me and thanked me for raising the two children,” she said. “He said it was his great honor in his life to meet me.”