This photo taken on January 3, 2018, shows Tran Trong Duyet, former director at the Hoa Lo Prison in Hanoi (dubbed the Hanoi Hilton), holding a photo in Haiphong of himself with U.S. captives at the prison, where former U.S. Navy pilot John McCain was held for more than five years after his jet was shot down over a Hanoi lake in 1967. (NHAC NGUYEN/AFP/Getty Images)

Among the tributes for the late U.S. senator John McCain, a number came from the country that, for better or worse, formed an integral part of his life story: Vietnam.

“When I learnt about his death early this morning, I feel very sad,” retired Vietnamese Col. Tran Trong Duyet was quoted as saying Sunday by Vietnam News.

During the Vietnam War, Duyet ran the Hoa Lo Prison, dubbed the “Hanoi Hilton" by American POWs. McCain, a Navy pilot, spent 5 ½ years in the prison after being shot down over Hanoi on a bombing mission in 1967.

The future senator would spend nearly half of those years in solitary confinement; the beatings he endured in the prison left him with physical problems that stayed with him for the rest of his life.

“I had a lot of time meeting him when he was kept in the prison," Duyet was quoted as saying after McCain’s death. “At that time I liked him personally for his toughness and strong stance."

Duyet also told Agence France-Presse that he admired McCain’s stubbornness and enjoyed arguing with him. “Out of working hours, we considered each other friends,” he said, adding that McCain had helped teach him English.

During a visit to Vietnam in 2000, McCain said that he could not yet forgive the guards who kept him at Hoa Lo Prison. “I still bear them ill will, not because of what they did to me, but because of what they did to some of my friends,” McCain said.

But despite this, McCain became one of the most vocal supporters of normalizing relations with the Communist-led Vietnam. In 1994, he co-sponsored a bill with then-Sen. John F. Kerry (D-Mass.) that called for ending economic sanctions against the country.

He would go on to make more than 20 visits to Vietnam in later years. During one trip in 2014, he noted that he received a warm welcome in the city where he had been held prisoner so long ago.

After McCain’s death Saturday at age 81, state-run outlets such as Vietnam News released articles that praised McCain for his work toward improving U.S.-Vietnamese relations.

On Monday, Vietnamese Foreign Minister Pham Binh Minh visited the U.S. Embassy in Hanoi and offered his own tribute to the late senator, calling him a “a symbol of his generation of senators, and of the veterans of the Vietnam war” in a message in a condolence book.

Vietnamese Ambassador to the United States Ha Kim Ngoc also praised McCain, telling Vietnam News that he could remember meeting the senator in the 1990s as he was working to improve relations with Vietnam.

“McCain deserves credit for promoting the Vietnam-U.S. relations and later, the comprehensive partnership between the two countries,” Ngoc was quoted as saying. The ambassador added that even during his illness, McCain paid attention to Vietnam-related issues.

At Hanoi’s Truc Bach Lake, a monument marks McCain’s capture there on Oct. 27, 1967. Over the past couple of days, a number of Vietnamese well-wishers and foreigners have visited the spot to pay their respects to the late senator, leaving flowers and incense at a makeshift shrine.

“Although he was once our enemy, he did a lot to help restore relations between the U.S. and Vietnam,” 60-year-old Hoang Manh Cuong told Bloomberg News. “That helped open the economy and improved our lives dramatically. We owe him for that.”

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