They’ve always been linked by Zaire and forever will be.

U.S. Olympic gold medalists. Repeat heavyweight champions. Men of deeply religious conviction.

American treasures.

It was 50 years ago today when they each stepped in that ring in Africa as adversaries, when 4-to-1 underdog Muhammad Ali stopped in his tracks and assured his cornermen this ring walk to meet the scowling George Foreman was not a funeral procession but a trek to immortality.

Solving the unsolvable and withstanding the might of Foreman’s destructive power punches for more than seven rounds, Ali executed the rope-a-dope by letting Foreman punch himself out before letting go with a beautiful, crushing onslaught that sent the giant to the canvas for good in the eighth round.

For Ali, the victory was vindication for his lonely, lengthy, principled, highly criticized – but just – stand against the Vietnam War, which left him absent from the ring during three of his prime years.

Add the “Thrilla in Manila” trilogy stoppage of Joe Frazier one year after this landmark “Rumble in the Jungle” triumph over Foreman, and Ali had sealed his reign as sportsman of the century and the best-known human on the planet. 

Leaving the ring as the loser that night was foreboding.

A deep cut over an eye that Foreman suffered during sparring in Zaire for the fight changed everything.

Because of a lengthy postponement, Foreman had to stay in Africa and endure another two months of Ali’s mind games that had endeared the challenger to the locals and moved them to incessant cheers of “Ali, bomaye!” (“Ali, kill him!”)

Beyond that, Foreman trainer Dick Sadler instructed all of the quality sparring partners to avoid hitting Foreman in the head for the six-week training period, meaning Ali’s fight-night salvos would be the first real punches sent that direction.

“He ran and trained, but the sparring was not real sparring,” Foreman’s longtime publicist and International Hall of Fame member Bill Caplan told BoxingScene.

Watching the Rumble in the Jungle from ringside, Caplan saw Foreman exhausted after throwing so many punches in the first two rounds.

“George’s style was to unload and go for early knockouts, and he’d destroyed the guys that had beaten Ali – Frazier and Ken Norton,” Caplan said. “But in this one, I said to the photographer next to me, ‘Oh my God, we’re going to blow this fight.’ I could see George starting to gas out.”

In defeat, Foreman was tasked with the unimaginable position that threatened to forever rank him as lesser than.

Ali and Don King wouldn’t grant a rematch – even after Foreman fought five men on one evening with “The Greatest” looking on in amusement.

Something inside Foreman ultimately cracked following a unanimous decision loss to Jimmy Young in 1977. He called it a religious awakening and made a lifelong conversion to preaching the gospel.

“I would say he was in depression, not knowing the time [it lasted] afterward … and when he had the religious epiphany and devoted himself to the church, he retired from boxing at 27 for 10 years,” Caplan said.

Caplan attended a few sermons of Foreman’s during the retirement, taking heart that Foreman was “in great spirits” by exchanging purse money for the lifting of souls.

Then, around 1986, Caplan’s late reporter friend, Allan Malamud of the Los Angeles Herald-Examiner, penned a story revealing that Foreman was back in the gym and training. That moved Caplan to board a flight to Houston and knock on Foreman’s door, to be greeted by the widely smiling former champion, who asked, “What took you so long?”

To think Foreman was going to fight again brought both joy and worry to Caplan. Was this a pie-in-the-sky venture? A novelty? What was the end game here?

Foreman, 37, weighed in at 267 for his March 1987 return bout, almost 10 years to the day of the Young loss. He fought Steve Zouski at Arco Arena in Sacramento.

Caplan assisted with the promotion and served as ring announcer, just as he had done when Foreman fought as an amateur in the Bay Area, exactly 20 years earlier and one year before winning gold in Mexico City.

“I was in charge of doing the hullabaloo announcing and caught myself saying, ‘In this corner, wearing red trunks with the blue stripe, weighing 267 pounds, former Olympic gold medalist, former heavyweight champion of the world …’ and as I’m saying that, I felt like it was a ‘Twilight Zone’ episode. Because I believed, after all those years, George was never going to fight again,” Caplan said.

“It was such a strange feeling … so absolutely happy. I never believed this would be happening.”

Foreman found Caplan afterward and said, “Well, I guess I can do it again,” after winning by fourth-round knockout and needing a one-fight provisional license just to get in the ring that night.

Following the bout, Foreman signed to be promoted by Bob Arum and proceeded on a routine schedule of fighting – nine bouts in 1988 alone – before landing (and losing) a competitive 1991 heavyweight title fight against Evander Holyfield.

It was a scintillating showing, a stirring preview of what was to come – the authoring of the most inspired athletic comeback for the ages.

“No world-class athlete has ever been retired for 10 years, come back and then competed at the championship level,” Caplan said.

On Nov. 5, 1994 – an astounding 20 years and six days after the “Rumble in the Jungle,” Foreman entered the MGM Grand Garden Arena in Las Vegas after telling his HBO broadcast colleague Jim Lampley that he was convinced he could throw body punches that would force then-heavyweight champion Michael Moorer to shift his body in position for Foreman to deliver a straight right to the face.

In the 10th round, Lampley exclaimed, “It happened!” as Foreman delivered a sudden right that dropped the young champion and made the 45-year-old Foreman the oldest heavyweight champion in history.

As Moorer was being counted out, Foreman peered upward to the heavens and then turned and sank to his knees in prayer.

Caplan, with a ringside seat to all of it, said he leaped to enter the ring right as Moorer hit the canvas, only to be withheld by two MGM Grand security guards.

Referee Joe Cortez counted, “Eight … nine … 10.”

“Now you can go,” one of the guards told the elated Caplan. 

“Twenty years later! No athlete has ever done that,” Caplan reminded. “Whatever I say next will not come across as profound and probably be read as cliched, but any one of us can do amazing things if you have your health and you believe in yourself.

“People might discourage you for one reason or another, but you can do it. And that was your proof.”

Foreman fully transformed from the scowling, destructive killer who battered Frazier – inspiring Howard Cosell’s unforgettable “Down goes Frazier!” chorus – and maintained a demeanor learned from former training partner Sonny Liston.

And then he converted to his true self – the lovable, jovial champ who made a fortune by hawking greaseless hamburger grills with humor and smiles.

He became close friends with Ali, exchanging regular phone calls through Ali’s battle with Parkinson’s before “The Greatest” died on June 3, 2016.

Foreman turned 75 on January 10, and he resides with his wife in Marshall, Texas. Both he and Ali had full-length feature films made about their lives.

In 1997, when the documentary feature, “When We Were Kings” – about the Rumble in the Jungle – won the Academy Award, both Ali and Foreman attended the ceremony and were ultimately summoned onto the stage by director Leon Gast.

Ali walked up first, hesitantly, with Foreman supporting him from behind by placing his right hand near Ali’s back.

“Ali’s shirttail had come out in the back, and as they were standing up there, George tucked Ali’s shirt in,” Caplan recalled. “Just such a sweet thing to do … something you would do for a friend.”