Muhammad Ali
Fights against Liston

By late 1963, Clay had become the top contender for Sonny Liston's title. The fight was set for February 25, 1964, in Miami Beach. Liston was an intimidating personality, a dominating fighter with a criminal past and ties to the mob. Based on Clay's uninspired performance against Jones and Cooper in his previous two fights, and Liston's destruction of former heavyweight champion Floyd Patterson in two first-round knockouts, Clay was an 8:1 underdog. Despite this, Clay taunted Liston during the pre-fight buildup, dubbing him "the big ugly bear", claiming "Liston even smells like a bear" and "I'm gonna give him to the local zoo after I whup him." Clay turned the pre-fight weigh-in into a circus, shouting at Liston that "someone is going to die at ringside tonight." Clay's pulse rate was measured at 120, more than double his normal 54. Many of those in attendance thought Clay's behavior stemmed from fear, and some commentators wondered if he would show up for the bout.

The outcome of the fight was a major upset. At the opening bell, Liston rushed at Clay, seemingly angry and looking for a quick knockout. However, Clay's superior speed and mobility enabled him to elude Liston, making the champion miss and look awkward. At the end of the first round, Clay opened up his attack and hit Liston repeatedly with jabs. Liston fought better in round two, but at the beginning of the third round Clay hit Liston with a combination that buckled his knees and opened a cut under his left eye. This was the first time Liston had ever been cut. At the end of round four, Clay was returning to his corner when he began experiencing blinding pain in his eyes and asked his trainer, Angelo Dundee, to cut off his gloves. Dundee refused. It has been speculated that the problem was due to ointment used to seal Liston's cuts, perhaps deliberately applied by his corner to his gloves. Though unconfirmed, boxing historian Bert Sugar said that two of Liston's opponents also complained about their eyes "burning".

Despite Liston's attempts to knock out a blinded Clay, Clay was able to survive the fifth round until sweat and tears rinsed the irritation from his eyes. In the sixth, Clay dominated, hitting Liston repeatedly. Liston did not answer the bell for the seventh round, and Clay was declared the winner by TKO. Liston stated that the reason he quit was an injured shoulder. Following the win, a triumphant Clay rushed to the edge of the ring and, pointing to the ringside press, shouted: "Eat your words!" He added, "I am the greatest! I shook up the world. I'm the prettiest thing that ever lived."

At ringside post fight, Clay appeared unconvinced that the fight was stopped due to a Liston shoulder injury, saying that the only injury Liston had was "an open eye, a big cut eye!" When told by Joe Louis that the injury was a "left arm thrown out of its socket," Clay quipped, "Yeah, swinging at nothing, who wouldn't?"

In winning this fight at the age of 22, Clay became the youngest boxer to take the title from a reigning heavyweight champion. However, Floyd Patterson remained the youngest to win the heavyweight championship, doing so at the age 21 during an elimination bout following Rocky Marciano 's retirement. Mike Tyson broke both records in 1986 when he defeated Trevor Berbick to win the heavyweight title at age 20. The feat also made Clay the fastest boxer to win the championship (non-vacant) in the modern era, doing so in 20 bouts.

Soon after the Liston fight, Clay changed his name to Cassius X, and then later to Muhammad Ali upon converting to the Nation of Islam. Ali then faced a rematch with Liston scheduled for May 1965 in Lewiston, Maine. It had been scheduled for Boston the previous November, but was postponed for six months due to Ali's emergency surgery for a hernia three days before. The fight was controversial. Midway through the first round, Liston was knocked down by a difficult-to-see blow the press dubbed a "phantom punch". Referee Jersey Joe Walcott did not begin the count immediately after the knockdown, as Ali refused to retreat to a neutral corner. Liston rose after he had been down for about 20 seconds, and the fight momentarily continued. However a few seconds later Walcott, having been informed by the timekeepers that Liston had been down for a count of 10, stopped the match and declared Ali the winner by knockout. The entire fight lasted less than two minutes.

It has since been speculated that Liston purposely dropped to the ground. Proposed motivations include threats on his life from the Nation of Islam, that he had bet against himself and that he "took a dive" to pay off debts. Slow-motion replays show that Liston was jarred by a chopping right from Ali, although it is unclear whether the blow was a genuine knockout punch.
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