Sonny Liston was a brute of a man. His fists measured fourteen inches in circumference. He could knock men out with his left jab. His opponents were given little chance of lasting 15 rounds, much less winning. So when a young, undefeated heavyweight named Cassius Clay, who would later be known as Muhammad Ali, challenged Liston, many critics worried about his safety. While “The Greatest’s” career has many hall of fame moments, none was more shocking or transforming than his upset of Liston.

At the time of the fight, Clay was not considered championship material; just a fleet-footed, motor-mouthed Olympic gold medalist known as the “Louisville Lip.” His recent ring performances left a little to be desired. In March of 1963, he eked out a decision over Doug Jones in a performance so shoddy that Sports Illustrated deemed him “an illogical contender.” Three months later, Henry Cooper sent him to the canvas in the fourth round. Clay managed to stop the papier-mâché faced Cooper on cuts in the fifth, but few were impressed.

Liston, on the other hand, had spent the late ‘50s and early ‘60s cleaning out the cream of the heavyweight division, not losing a fight in more than 8 years. When he finally earned a title shot with Floyd Patterson in September of 1962, Liston needed just two minutes and five seconds to take the belt. For their rematch in July of the following year, it took him four seconds longer.

Having demolished most contenders in his quest for the title, Liston needed fresh meat for his next bout. He did not have to look far. The irrepressible Clay had stalked him for a chance at the title, jeering and taunting, and garnering headline every step of the way.

Liston finally agreed to face him in Miami, Florida, on February 25, 1964. So confident was Liston, he told Clay he would kiss his feet if the fight went more than three rounds.

Clay paid him no mind and kept gabbing until the opening bell. Pre-fight weigh-ins are notoriously dull, but Clay showed up for this one in peak theatrical form, calling Liston “a big, ugly bear” and predicting that people at ringside would die of shock.

Boxing writers and fans may have given Clay the edge in showmanship, but few gave him a chance in the ring. He was an 8-1 underdog, and promoters had trouble selling tickets to the fight. A paltry 8,297 people showed up at Miami’s Convention Hall to watch the bout.

When round one began, Liston charged and Clay backpedaled. Those at ringside initially thought Clay was scared, but as the round went on, it became apparent that he was using his welterweight legs and height advantage to dictate the pace of the fight. Clay kept his distance, letting Liston’s left hooks whiff by. On occasion, he would briefly plant his feet to perform pugilistic surgery.

Clay used this same tactic through the next two rounds. At the end of third, Liston did not kiss Clay’s feet. He did, however, have a small cut under his left eye.

Liston’s handlers applied a coagulant to the cut, some of which ended up on his glove. Whether or not it was intentional is one of the many mysteries surrounding Sonny Liston. At the end of the fourth round, Clay returned to his corner blinded and panicked, with serious reservations about continuing. His trainer Angelo Dundee, seeing clearly, and knowing was at stake, said, “This is for the big one,” as he pushed Clay to the middle of the ring for the start of round five.

The fifth round remains one of the great escape acts in boxing history. Liston, smelling blood, attacked, thwacking Clay several times with his vaunted left hook. But he learned, as we all eventually would, that Clay had a chin of stone. By the end of the fifth round, his eyes had cleared up.

Liston was not used to this kind of pace. His fights had been so one-sided that he had fought a total of six rounds in four years. He came out of his corner for round six breathing heavily.

His shoulder was getting sorer as well. Rounds and rounds of pounding air instead of Clay had taken its toll on his shoulder. Throughout the sixth, Clay punched Liston with ease.

When the bell sounded for the seventh, he remained his on his stool, his shoulder spent and his best punches gone. Clay stood up, shuffled his feet, and pointed to all the naysayer sportswriters who sat at ringside.

“I shook up the world,” he repeatedly screamed.

At the time, neither he, nor we, knew just how right he was.