It never failed. The sound of death came punctually, reliably, at 9 p.m. each night.
It reverberated on the grounds of the notorious La Cabaña prison in Havana, where the men who had dared to defy the rules of the Castro regime, denouncing oppression and calling for liberty, had been hauled. At the same hour, each night, they were forced to hear what happens to people like them.
“Ready, aim, fire!” they’d hear the execution squads bellow from outside, just beyond their barracks, as their fellow political prisoners – some of them their brothers, fathers, sons – cried out “Viva Cuba Libre!” (“Long Live a Free Cuba!”) and “Viva Cristo Rey!” (Long Live Christ the King!”).
Then they heard the firing squad discharge their rifles just as the thunderous 9 p.m. cannon-shot re-enactment rang out and reverberated around Havana, a historical ritual in Cuba that delighted tourists.
“The firing squads did their killing at 9 p.m., so that the cannon shot would mask the noise of their rifles,” recalled Luis Israel Abreu, a 78-year-old exile who spent 14 years as a political prisoner, several of those years at La Cabana.
“Then you’d hear a separate shot, the coup de grace,” said Abreu, whose blue eyes still well with tears at the memory. “They wanted to make sure they were cold dead.”
Today, nearly 50 years after Abreu was thrown in jail for joining a group of disillusioned supporters of the Cuban revolution who fought for democratic ideals in their homeland, more than 100 people are believed to be held in Cuba’s jails for their dissidence. And international human rights groups, whose requests to visit the jails always have been denied, say abuse of political prisoners and inhumane conditions persist.
Among the dissidents' most ardent supporters are former political prisoners who know their plight, and have devoted most of their lives in exile to building international pressure for their release.
These days, in particular, Abreu, a co-founder and executive director of Committee to Aid Human Rights Activists, devoted to pressing for democratic reform in Cuba, is focusing his energies on a group of political prisoners who Fidel Castro’s brother, Raul – now the president – indicated through third parties he would release soon.
The prisoners are part of a group of more than 70 dissidents, independent journalists and others who were accused in a massive 2003 crackdown of counter-revolutionary activities and trying to undermine the government, and given long sentences.
Most of those arrested and jailed in 2003 have been released under international pressure that grew after the death of Orlando Zapata Tamayo, a plumber and bricklayer who staged an 82-day hunger strike to protest what he said were beatings by guards.
Most were forced to leave Cuba as a condition of their release. Some refused, saying they did not want to “sell out” to what they said was the government’s attempt to rid the island of dissenting voices.
Just under a dozen of the 2003 group are said to remain in jail. Human rights groups, such as Human Rights Watch, believe that in addition to them, more than 100 people are in Cuban jails because of their activism against oppressive government policies. The U.S. State Department's report on Cuba says that "in addition to as many as 5,000 people" may be in jail after having been "sentenced for 'dangerousness,'" a term the regime often uses to describe people who are vocal in their criticism of the government.
“So much of this world of political prisoners in Cuba remains unknown outside Cuba,” said Abreu. “Human rights groups are not allowed in there, these people suffer in the dark, like we did.”
In a recent interview, Abreu described what being a political prisoner in Cuba was like for him from 1961 to 1975, years he spent in five of the most brutal jails, labor camps and hospitals.
Sitting in a first-floor room of an old, but neatly-kept building in Union City that serves as the headquarters of the Former Cuban Political Prisoners organization, Abreu recalled that fateful day in 1961 when he changed his plans to try to escape Cuba and attended a dissidents meeting.
“A bunch of us had been ardent supporters of Castro and the revolution,” Abreu, a retired accountant who still wears suits, freshly ironed shirts and ties. “We had organized against [former Cuban leader Fulgencio] Batista.”
“But it became painfully obvious that the revolution was not what had been promised, and we were not free,” he said. “So we organized again, this time in opposition of the revolutionaries we had so much hope in.”
The timing was bad for Abreu.
Government security officials, he said, had learned about the clandestine meeting and raided it, arresting everyone there, including him.
They took him to La Cabaña, built in the 18th century. They put 200 men in a space meant for 60, he recalled. They provided only one toilet for the more than 200 men.
“We’d line up to go to the bathroom,” he said. “Invariably some of us just went on ourselves. They knew this would happen, the government officials. It was all part of driving you to desperation, of making you feel like less than a street animal.”
Frequently, the prisoners were pressured to agree to go to another location for a “re-education,” a process for indoctrinating them and getting them to pledge their loyalty to communist ideals and their disdain for the regime’s critics and ideological opposites.
Abreu refused and was made to pay for it.
He and others who resisted were made to go through daily gauntlets at the jail. During the daily headcounts, guards lined up on either side of the prisoners and beat them as each one walked past, on their way back to their cells.
“They’d hit us with bayonets,” Abreu said.
They would spike their food with laxatives, and bring in patients from psychiatric hospitals and let them scream and sing at all hours of the day and night.
“The nuts drove us nuts,” Abreu said. “To go without sleep, and then to hear these people screaming nonsense. They were taken back to their hospital after about two weeks.”
The most recalcitrant were taken to a labor camp, where they were made to break stone and rip out weeds in the intense heat and were beat with bayonets or machetes while they toiled, Abreu said.
“They did everything to drive us up a wall so we’d give up and go through the re-education,” Abreu said. “Some people did, they felt they were going to go mad and were ready to agree to anything.”
But Abreu held firm, and suffered serious beatings, sometimes landing him in the hospital.
“One day some of my fellow political prisoners and I at the labor camp just decided we were not going to do the forced labor,” Abreu said. “I thought ‘They beat us if we work, so I won’t, what’s the difference.’”
The difference was the worst beating he had suffered yet, he said.
A burly guard known as “Girón” pushed Abreu to the ground, pressed his bayonet into a wound he had on his backside, and pushed it deep in the wound, rotating the bayonet.
“It must have pierced even my bone,” Abreu said. “The pain was excruciating, unspeakable. I tried to hypnotize myself as I felt myself feeling faint, coming to, losing consciousness, coming to again.”
“I said to myself ‘They can’t do more than this, except kill me, and killing me, for some reason, didn’t seem to be in their plans,” he said.
Girón.pricked Abreu nearly 100 times with the bayonet, causing such blood loss, Abreu said, that he was taken to the hospital.
At the end of Abreu's 12-year sentence, Cuban authorities had news -- he had been sentenced an additional two for his uncooperative behavior, he said.
"They said I was a danger to the revolution, and they didn't want to risk putting me back out in the streets because I had not been cured of my political dissidence," Abreu said.
Finally, as part of a plan to expel some of its most ardent opponents from the island, the Cuban government allowed Abreu and other former political prisoners to leave in the late 1970's. Abreu left to Spain and after four months arrived in the United States.
The walls of the main office of the Former Cuban Political Prisoners organization are filled with framed photos of dozens of mostly men who are said to have been killed in Cuba for their human rights activism. Within these walls, for decades and decades, Abreu and other former political prisoners have met weekly to talk about bringing democratic change to Cuba.
When there were more Cuban exiles in Union City, in the 1960's and 1970's, the men organized marches and rallies and vigils that drew scores of fellow countrymen who felt that the regime would not last much longer.
Now that most of those Cuban exiles have left the area, for Florida or the suburbs of New Jersey, they fight most of their daily anti-regime battle online -- sending emails and Facebook and Twitter messages about freedom and news about political prisoners.
“I don’t feel that I did anything extraordinary,” Abreu said of his time in Cuban jails. “There are dissidents who spent 30 years in prison because they wanted freedom for Cubans and fought for it. My 14 years are a small amount of time compared to what they endured.”
Abreu scans the framed pictures on the walls of those who didn't make it out of the prisons in Cuba, and his steady demeanor cracks.
As the rims of his eyes turn red, he says he continues the fight because, in his mind and his heart, he made a pledge to these dissidents.
"I said I wouldn't let their death be in vain," he said. "I said I'd never give up the fight until all the political prisoners are free in Cuba."
"I have not rested because the causes for which I fought and gave up so much still are necessary," he said. "The oppression, the human rights violations, are still alive, they still persist. There is no liberty yet in Cuba."
Elizabeth Llorente is Senior Reporter for FoxNews.com, and can be reached at Elizabeth.Llorente@Foxnews.com. Follow her on Twitter @Liz_Llorente.