By Ju-min Park and James Pearson

SEOUL (Reuters) - As autumn descended on a Korean countryside devastated by three years of intense war, a group of anti-communist guerrillas presented U.S. serviceman Merrill Edward Newman with a gold ring. It was September, 1953.

For Newman, the ring became a proud symbol of the role he played as an adviser to a group of battle-hardened partisans who fought deep behind enemy lines in a war that pitted the China- and Soviet-backed North against the U.S.-backed South.

Now, six decades on, the 85-year-old pensioner who lives in a retirement community in California, has become one of the last prisoners of that war. He returned to North Korea last month as an American tourist and was snatched by authorities from his plane moments before it was due to depart for Beijing.

When he returned to the isolated state, he was taking a risk, former guerrillas who knew Newman said. The North Korean regime has nourished memories of the 1950-53 Korean War as the inspiration for the country's identity and acts as if the conflict is still happening.

Technically, the war did not end. No peace treaty was signed between the United States, South Korea and North Korea.

On Saturday, North Korea released a video showing the pensioner reading a handwritten confession of his role in the war. The North's KCNA news agency said he was a mastermind of clandestine operations and accused him of killing civilians during the war.

"Those bastards already knew Newman before the war was over," said Kim Chang-sun, one of the men who presented Newman with the ring in 1953. Kim was still at school when he joined the 'Kuwol' Partisan Regiment, a force that Newman trained, he said in an interview in Seoul.

"They obtained the roster of our entire regiment," Kim said.

The 'Kuwol Regiment', or 'Kuwolsan' in Korean, meaning 'September Mountain,' was named after a mountain in western North Korea where the guerrillas sought refuge as soldiers of the North's Korean People's Army (KPA) swept down the Korean peninsula when war broke out.

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From there, the partisans fought their way to North Korea's west coast and sailed to offshore islands where they launched last-ditch battles against the North Korean army.

WHITE TIGERS

The Kuwol Regiment was just one of many groups of anti-communist partisans that were under the command of the U.S. Army 8240th Unit, nicknamed the 'White Tigers'.

The White Tigers co-ordinated some of the most daring missions of the Korean War, embedding undercover agents deep in enemy territory - sometimes for months at a time - spying on and disrupting North Korean wartime operations, according to documented histories of the regiment.

The unit, whose existence was classified until the early 1990s, was the predecessor to U.S. special forces. Members of the White Tigers were handpicked from the U.S. Army, and not told about their mission until they arrived in Seoul.

"The advisers mostly stayed behind after sending Korean partisans into the North - mainly because Americans would be so easily recognized - but some of them did accompany partisan units and engage in combat," Bruce Cumings, an expert on the Korean War at the University of Chicago, told Reuters.

Ben S. Malcom, a retired U.S. Army Colonel, was one such adviser - a fellow White Tiger who served alongside Newman and led several raids along the North Korean coast.

He was awarded a Silver Star in March 1953 for bravery, but never received a badge marking his combat in the Korean War - the U.S. Army did not officially recognize special operations as combat.

"As soon as I lifted the receiver to my ear I stepped across that line separating the regular army from the clandestine army," Malcom wrote in his 1996 memoirs, describing a call he received from a commanding officer during the war.

"I went from being another faceless name on an army roster to a handpicked player in a unique operation about which few Americans knew anything," he wrote.

NEWMAN VISITS SEOUL

Soldiers who fought alongside Newman said he wore his commemorative ring when he visited South Korea after the war. He went there twice in the 2000s.

On one of these trips, he paid tribute at the National Cemetery to fallen friends. He was reunited with his old comrades over drinks and food and travelled with them to the border island that was headquarters of his unit when fighting ended.

Kim Hyeon, a member of the Kuwol Regiment who kept in contact with Newman and visited his family in California in 2004, was on a boat deep in North Korean-held territory on a summer afternoon in 1953, just weeks before a cease fire was agreed.

"At 1 o'clock on July 15, partisans used an operational boat to get within 50 meters of the North Korean coast under Lt. Newman's instruction," reads a book about the unit edited by Kim.

They picked up an agent and returned to an island outpost used by the partisans from the early months of the war, the book said. When the armistice was signed 12 days later, the men left the island behind and sailed south to freedom.

Kim has exchanged letters and emails with Newman, and they became close friends. But if he were Newman, he said, he would not have gone back to North Korea.

"In the eyes of the North Koreans, he would have literally been a spy engaging in some kind of espionage activity ... I wouldn't go there (if I were him)," Kim, now 86, told Reuters.

"Our members were working, fighting and engaging in espionage alongside Newman because he was an adviser," he said.

The Kuwolsan soldiers are well known in South Korea, and are depicted in popular culture as heroes in the fight against communism. The regiment and its guerrillas were the subject of a 1965 film called 'Blood-soaked Mt. Kuwol'.

Kim Chang-sun, the former rank-and-file partisan member, recalled Newman as a big American military officer with a warm heart who supervised their training and landing operations.

"He had this U.S. army food box and shared that with us. He stayed with us at a bunker," said Kim, now 81.

"They detained him because he served in the Kuwol regiment. He is just a very bad guy for them," Kim said, referring to the North Korean authorities.

It is not entirely clear why Newman took the risk of visiting North Korea. But evidently the war and his former comrades had left a deep impression on him.

"Kuwolsan was among the most effective guerrilla warfare units," he wrote in a congratulatory message attached to a book published by the Kuwolsan Guerrilla Unit Comrade Association in Seoul.

"I am proud to have served with you."

(Editing by Jack Kim and Raju Gopalakrishnan and Neil Fullick)