On March 13, 1973, former CIA employee John T. Downey speaks during a news conference in New Britain, Conn. He spent 20 years as a prisoner in China during the Cold War. (Bob Child/AP)

John T. Downey, who joined the CIA after college and was captured and held prisoner in Communist China for more than 20 years on espionage charges — one of the most harrowing chapters of the Cold War — died Nov. 17 at a hospice in Branford, Conn. He was 84.

His son, John Lee Downey, confirmed the death. He said his father, a retired judge in New Haven, Conn., had pancreatic cancer and Parkinson’s disease.

Mr. Downey’s imprisonment, which included long stretches of solitary confinement, lasted from 1952 until his release in 1973. Back in the United States, he was heralded as one of the country’s foremost symbols of patriotism and fortitude. A newly minted Yale student-athlete when he was seized, he was a frail 42-year-old upon his liberation.

“He was so matter-of-fact,” his son said in an interview Monday. When an article about him was published by Slate earlier this year, describing his story as “incredible,” he was somewhat abashed, and in a private conversation with his son allowed that it “made him sound too heroic.”

But his resolve and endurance evoked adulation among old friends, neighbors and schoolmates, as well as those at high levels of the government. Catholic schools in Connecticut, his home state, prayed constantly for his release.

He quickly got on with his life, graduating from Harvard Law School, marrying and becoming a father.

Although Mr. Downey was afflicted for years by illness, his outlook was essentially one of appreciation for the life he was able to lead after coming home. “I never expected to have any of this,” he told his son in a private moment late in his life.

John Thomas Downey, who was known as Jack, was born April 9, 1930, in Wallingford, Conn. At 8, he moved to New Britain, Conn., after his father, a probate judge, was killed in a car accident. His mother supported the family by working as a middle school teacher.

He graduated in 1947 from the private Choate school in Wallingford, Conn., and in 1951 from Yale, where he was a member of the football, wrestling and rugby teams.

After a brief period of CIA training, Mr. Downey was dispatched to Japan to take part in the agency’s operations against China. At the time, the nation was embroiled in the Cold War, engaged in armed conflict on the Korean Peninsula, while Communism, as championed by Soviet Russia and China, appeared to represent a worldwide menace.

“It felt like the future of mankind was at stake,” Mr. Downey told Slate.

Histories of the U.S. intelligence effort in the early years of the Cold War reveal efforts to conduct operations inside areas under Communist domination, including the Soviet Union and China. Most, if not all of these efforts were reported to have ended in disaster.

Mr. Downey and a second operative, Richard G. Fecteau, were flown in a C-47 into China to pluck another operative from the ground and bring him back. The plane was shot down over Manchuria on Nov. 29, 1952, and the two pilots, Norman Schwartz and Robert Snoddy, died at the scene.

“We were caught in a classic ambush,” Mr. Downey told People magazine in 1978. “I found out later at our trial that our Chinese radio operator had been forced to cooperate.”

Months of solitary confinement in a 5-by-8-foot cell in Beijing followed. Then came a trial at which Mr. Downey was sentenced to life imprisonment; Fecteau received a term of 20 years. Years passed with only occasional interruption of his solitary confinement.

Based on an internal CIA documentary that was ultimately made public, a turning point in his psychological state occurred after about four years of captivity.

“I just pulled myself together and said, ‘Enough of this crap,’ ” he later told the filmmakers. “I really found the most pernicious thing in prison was feeling sorry for yourself.”

He and Fecteau also told the CIA that they learned not to complain about treatment. When Fecteau said tomatoes gave him indigestion, he’d get more tomatoes. If he said the weekly bath didn’t have enough water, he’d get less water next time.

Developing a strict routine, to which Mr. Downey tried to adhere for the remaining years of his confinement, he took up a variety of activities including a fitness regimen that sometimes included up to 10 miles of jogging a day, Bible reading and trying to learn Russian and French.

“I was given some pages from U.S. newspapers, Sports Illustrated, the Yale alumni magazine and sometimes the New York Times book section,” he told People. “You get good at piecing together clues. I learned about the moon walk 18 months afterward from a little ad on a sports page, advertising 8x10 glossies of the astronauts on the moon.”

Matters began to change quickly between the United States and China in 1971. It was the year of the table tennis competition in China between teams from each nation. The games were called ping-pong diplomacy, and they began the thaw in relations between the nations.

After the matches, and the stunning diplomatic developments that followed, Fecteau was freed, and Mr. Downey’s sentence was reduced.

Still, China demanded that the United States admit that Mr. Downey worked for the CIA. The United States refused, until President Richard M. Nixon admitted to it in 1973. He did so at a news conference with a seeming casualness that continues to raise questions as to whether it was artful or accidental.

Mr. Downey was released on March 12, 1973. At a news conference in Connecticut shortly afterward, he displayed the approach to his ordeal that he would continue throughout his life.

“When you talk about 20 years in a lump sum, it sounds like a big deal,” he told reporters. But, he said, “On a day-to-day basis, you just learn to go along.”

He earned a law degree in 1976 and began a career largely devoted to public service before he went on the bench in New Haven, where he handled many cases involving juvenile offenders. He officially retired in 1997.

In addition to his son, of Philadelphia, survivors include his wife of 39 years, Audrey Lee Downey of New Haven, and a brother.

Over the decades, Mr. Downey and Fecteau, who became Boston University’s assistant athletic director, were given many CIA honors. They received the Distinguished Intelligence Cross, one of the highest awards for valor, in 2013.

Mr. Downey said at the time, “We’re at the age where, if you want to call us heroes, we’re not going to argue anymore, [but] we know better.”