Win Tin and Burma democracy leader Aung San Suu Kyi in 2011. (Nyein Chan Naing/EPA)

Win Tin, an uncompromising Burmese journalist who helped Aung San Suu Kyi launch a pro-democracy movement against the brutal military regime and then endured nearly two decades in jail as one of his country's longest-serving political prisoners, died April 21 in Rangoon. He was 84 according to most sources, although others cited his age as 85.

The National League for Democracy party, which Mr. Win founded with Nobel Peace Prize winner Suu Kyi, announced the death.

Mr. Win suffered from respiratory problems and other ailments that largely were left untreated during his 19 years in prison before his release in 2008. He had been one of the world’s longest-detained reporters, according to the Committee to Protect Journalists.

For Mr. Win, who came of age in Burma under British rule, the urge to dissent was long ingrained in his character. As a teenager, he tried to join Gen. Aung San’s Burmese resistance army but was politely rebuffed by the man who would become a national hero during the independence struggle.

“Aung San plainly said, ‘Stick with your studies. There are many people to fight. The time will come for you,’ ” Mr. Win once recalled. Aung San, the father of Aung San Suu Kyi, was gunned down shortly before independence was achieved in 1948.

Win Tin, a former political prisoner and an opposition party stalwart, at his home in Yangon in 2013. (Gemunu Amarasinghe/AP)

Burma, also known as Myanmar, descended into absolute military rule starting in 1962 and became a pariah state because of the junta’s human rights violations and repression of civic society.

Mr. Win served as top editor of the independent Burmese newspaper Hanthawati in Mandalay before dictator Ne Win shuttered it in the late 1970s.

“The reason I became a politician is because of military governments,” Mr. Win told the Agence France-Presse news service last year. “They seized the newspapers and publishing houses. As I have many contacts in politics, I reached into politics.”

He became part of the circle of intellectual advisers that coalesced around Suu Kyi, who called for nonviolent resistance and who was embraced as the country’s greatest hope in generations for freedom. Mr. Win was nicknamed “Saya,” or “teacher,” an indicator of his esteem in anti-military politics.

The National League for Democracy won an overwhelming victory in the 1990 general election but was not permitted by the junta to govern. The crackdown on NLD leaders had already begun.

Suu Kyi, who spent much of her life abroad before returning to Burma in 1988 to care for her dying mother, was placed under house arrest for much of the period between 1989 to 2010.

Mr. Win was thrown into prison in 1989, having been charged with being a member of the banned Communist Party of Burma.

“Immediately after his arrest, U Win Tin was kept without food and sleep for three days,” Suu Kyi once wrote. “It appeared the interrogators wished to force him to admit that he was my adviser, in other words, my puppet master. A man of courage and integrity, Win Tin would not be intimidated into making false confessions.”

To Mr. Win’s initial three-year prison sentence, the government repeatedly added new charges.

He was given five years for “misappropriation of state property” when guards found a pencil and paper in his cell. He received seven more years for “secretly publishing propaganda to incite riots in jail” after smuggling a letter to the United Nations about inhumane prison conditions.

He was beaten and held for six months in a former kennel for prison dogs in Rangoon’s Insein jail and later transferred to another prison, where harsh treatment continued. He endured years of isolation and used ink made of brick powder and water to write poems and political musings on the wall.

According to the Committee to Protect Journalists, Mr. Win had at least two heart attacks during his confinement and suffered from high blood pressure, a degenerative spine condition and diabetes. He repeatedly refused to sign confessions that, he was told, would hasten his release.

The ailing Mr. Win, then 78, was freed unexpectedly in 2008 during the release of 9,000 inmates, most of them thought to be petty criminals.

David Steinberg, an emeritus professor of Asian studies at Georgetown University and an expert on Burma, called Mr. Win “the most articulate spokesman of the elder group of advisers” working with the National League for Democracy. “When he got out of prison, he was very forceful,” Steinberg said. “He had this reputation for being autonomous and independent.”

The United States began lifting sanctions and recognized the country diplomatically as Burmese leadership transitioned to a quasi-civilian government. Suu Kyi was elected to parliament in 2012.

Mr. Win remained a steely foe of the military that still dominated the government and criticized Suu Kyi for making conciliatory overtures to her former tormentors.

“Some of us would like to push the military into the Bay of Bengal,” Mr. Win told The Washington Post last year. “She only wants to push them into Kandawgyi Lake,” a reference to a lake in the former capital city of Rangoon.

Win Tin was born March 12, 1930 (some sources say 1929), in a village north of Rangoon. As a young man, he attended Rangoon University and began a long career in journalism and publishing. He never married.

Emerging from prison, Mr. Win’s teeth were rotting and his body was crumbling. He found his home and possessions gone. He wrote a memoir, “What’s That? A Human Hell,” published in 2010, that detailed his more than 7,000 days in prison.

He said he would continue to wear his blue prison uniform until all political prisoners, estimated last year at fewer than 100, were released. There were reports that he risked going back to jail for not returning his prison-issue clothing or paying the $2 to buy them.

“I remember Daw Suu Kyi’s response to this kind of warning about her security,” he said, referring to the Nobel laureate. “She said, ‘If a quack shoots me with a pistol, then the whole world will know where this bullet comes from.’ ”