The early years

The man who would go on to become arguably the greatest sporting colossus the world has ever seen and every bit as significant a 20th-century icon as JFK, Marilyn Monroe and Frank Sinatra was born Cassius Marcellus Clay Jr into a poverty-stricken family in Louisville, Kentucky during the Second World War.

Born on January 17, 1942, to Odessa and Cassius Sr, a sign painter by trade, Clay, later Muhammad Ali, but a man who will forever be known as "the Greatest", made a chance step into boxing after having his bike stolen – a 12-year-old Clay promised to "whup whoever stole it".

In an attempt to channel his aggression, the policeman he reported the crime to, Joe Martin, who also trained young boxers at a local gym, is said to have told him. "Well, you better learn how to fight before you start challenging people."

Ali started working with Martin to learn the ropes, and so began the boxing career of a man whose life story would encompass not just sport, but issues of racial equality, religion, politics and even war.

Clay's big breakthrough came at the age of just 18 when he won the light-heavyweight gold medal at the 1960 Olympics in Rome. However, in an early sign of the struggles outside the ring that he was to devote so much of his life to, Clay found that, upon returning home, he was not immune to the racism that so bedevilled American society.

After being refused service by a waitress at a "whites-only" restaurant, and then fighting with a white gang, a disgusted Clay reportedly threw his gold medal into the Ohio River.

Clay turned professional in October of the same year and won fans and enemies in equal measure as he ploughed his way through the heavyweight division ridiculing his opponents, who he called "bums" in the process.

The young pretender with the trash talk?

By late 1963, Clay had become the top contender for the world heavyweight title held by Sonny Liston, a fighter with a fearsome reputation who was for a time widely thought to be unbeatable.

The fight was set for February 25, 1964 in Miami. Liston was an intimidating personality, a brutal, dominating fighter with a criminal past and ties to the mob, a boxer who was in many ways viewed as the Mike Tyson of his day.

Based on Clay's uninspired performance in the two fights leading up to his battle with Liston, notably being knocked to the canvas by England's Henry Cooper, and Liston's ruthless destruction of former heavyweight champion Floyd Patterson, the young pretender was a rank outsider. Some pundits even took the view that the trash-talking Clay had largely talked his way into a shot at the world title.

The challenger taunted Liston during the pre-fight build-up, dubbing him "the big ugly bear".

"Liston even smells like a bear," Clay said. "After I beat him I'm going to donate him to the zoo."

Clay turned the pre-fight weigh-in into a circus, shouting at Liston that "someone is going to die at ringside tonight". Many of those in attendance at the weigh-in thought Clay's behaviour stemmed from fear, and some commentators wondered if he would even show up for the bout.

The result was a huge shock. Clay out-boxed and outsmarted the champion, who was made to look awkward and ungainly with a series of missed punches.

But at the end of round four, as Clay returned to his corner, 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, which it was claimed, although unproven, was deliberately applied by Liston's corner to his gloves. Despite Liston's attempts to knock out a blinded Clay, Clay was able to survive the fifth round.

In the sixth, Clay dominated, hitting Liston repeatedly. The champion failed to come out for the bell for the seventh round, and Clay was declared the winner by a technical knock-out.

By winning this fight at age 22, Clay became the youngest boxer to take the title from a reigning heavyweight champion and set the scene for the rise and rise of an icon.

Conversion to Islam and name change

In the aftermath of taking the heavyweight crown, Clay changed his name to Muhammad Ali and joined the Nation of Islam, an institution that much of the world had not even heard of and understood still less.

Ali then faced a rematch with Liston in May 1965 in Lewiston, Maine – a fight that to this day still stands out as one of the most controversial in the historical annals of boxing.

The fight was most notable for the "phantom punch" that floored Liston midway through the first round. Ali was declared the winner by knockout, with the entire fight lasting less than two minutes.

It has since been speculated that Liston "took a dive" to pay off debts or because of threats to his life from the Nation of Islam. Whatever the truth of such claims, Ali's second victory over Liston had effectively demolished the reputation of a fighter who had dominated the division.

Fights outside the ring

Despite Ali's dominance of the sport, trouble was looming large outside the ring with a chaotic personal life and the disintegration of his marriage to his first wife Sonji Roi. Roi left him after little more than a year of marriage, claiming he had coerced her into adopting Muslim dress and customs.

Meanwhile, Ali and another heavyweight champion Ernie Terrell had agreed to meet for a bout after the World Boxing Association, one of the sport's two governing bodies, had stripped Ali of his title afer he joined the Nation of Islam. Ali fought Terrell in Houston on February 6, 1967. Terrell, who during the lead up to the bout repeatedly called Ali "Clay", much to the annoyance of Ali who described it as his "slave name".

In a brutal display, Ali taunted Terrell shouting between punches: "What's my name ... what's my name?", before wing a unanimous 15-round decision.

In 1967 Ali married Belinda Boyd, who converted to Islam and changed her name to Khalilah Camacho-Ali after their wedding.

In the same year it was Ali's outspoken views and stance against the Vietnam War that was to propel him into what was arguably the biggest fight of his career.

Drafted into the military in April 1967, he refused to serve on the grounds that he was a practicing Muslim minister with religious beliefs that prevented him from fighting.

Famously stating that he had "no quarrel with them Vietcong".

"My conscience won't let me go shoot my brother, or some darker people, or some poor hungry people in the mud for big powerful America," said Ali at the time.

"And shoot them for what? They never called me ni**er, they never lynched me, they didn't put no dogs on me, they didn't rob me of my nationality, rape or kill my mother and father ... How can I shoot them poor people? Just take me to jail."

He was arrested for committing a felony and almost immediately stripped of his world title and boxing licence.

The US Department of Justice pursued a legal case against Ali, denying his claim for conscientious objector status. Ali was found guilty of violating selective service laws and sentenced to five years in prison in June 1967, but remained free while appealing his conviction. Unable to compete professionally in the meantime, Ali missed more than three prime years of his career. The US Supreme Court eventually overturned the conviction in June 1971.

During his time of inactivity, as opposition to the Vietnam War began to grow and Ali's stance gained widespread public sympathy, he spoke at colleges across the nation, criticising the Vietnam War and advocating African-American pride and racial justice.

It was perhaps this hiatus from the ring more than anything else that led to Ali being viewed as simply more than a boxing icon and one whose actions transcended the world of sport.

The comeback and bitter enemies

By the time Ali returned to the ring in 1970, the heavyweight division was arguably the most fiercely contested ever, with several big-punching fighters all vying for supremacy.

The title was now held by Joe Frazier a ferocious fighter who would go on to play a key role in the Ali's life story due to three fiercely contested bouts.

After a handful of comeback fights, Ali took on Frazier in 1971 in what has been called the "Fight of the Century" staged at New York's Madison Square Garden. A star-studded crowd saw the pair slug it out for 14 rounds before Frazier flattened Ali with a vicious left hook in the 15th.

Ali recovered quickly, but the judges awarded the decision to Frazier, handing Ali his first professional loss after 31 wins. He soon suffered a second loss, to Ken Norton, a fight that saw the former champion suffer a broken jaw.

However, Ali would go on to beat Frazier in a non-title 1974 rematch that would put him back in contention. It was later that year though that Ali was to have the defining fight of his career and what, even now, is seen as one of the sport's most iconic bouts.

Billed as the "Rumble in the Jungle", Ali was pitted against undefeated heavyweight champion George Foreman, who had already decisively defeated Frazier.

The bout was organised by promoter Don King and held in Kinshasa, Zaire, with Ali seen as the underdog to the younger and much bigger Foreman.

In a boxing upset that rivalled his victory over Liston a decade earlier, Ali silenced his critics with an emphatic win. He baited Foreman into throwing wild punches with his "rope-a-dope" technique that allowed Foreman to get him against the ropes and swing away until he tired himself out, before stunning his opponent with an eighth-round knockout to reclaim the title.

The fight is viewed by boxing observers as being one that heralded the start of big money in the sport. It is also viewed as the high watermark of Ali's career, largely due to his overcoming of Foreman, who was considered one of the hardest and most brutal punchers in heavyweight history. Foreman, reflecting on the fight would later, said: "I'll admit it. Muhammad outthought me and outfought me."

There was to be a third and final clash with Frazier as the two men locked horns for a grudge match in Quezon City, Philippines, in 1975. Dubbed the "Thrilla in Manila", the bout nearly went the distance, with both men delivering and absorbing tremendous punishment.

Frazier's trainer threw in the towel after the 14th round, giving the hard-fought victory to Ali.

An ailing Ali said afterwards that the fight "was the closest thing to dying that I know", and, when later asked if he had viewed the fight on videotape, reportedly said, "Why would I want to go back and see Hell?" After the fight he cited Frazier as "the greatest fighter of all times next to me".

It was soon after the final fight with Frazier, that Ali divorced his second wife Khalilah, who had four children Maryum, born a year later, Jamillah and Liban, both born in 1970, and Muhammad Ali Jr, who arrived in 1972.

Decline in and out of the ring?

If Ali's victories over Liston and Foreman were to represent the zenith of his illustrious career, the third and final battle with Frazier should perhaps be viewed as the beginning of the end.

After eventually losing his heavyweight title to Leon Spinks in February 1978, Ali defeated him in a rematch in September of the same year, becoming the first boxer to win the heavyweight championship three times.

Following a brief retirement, he returned to the ring to face Larry Holmes in 1980, but was mismatched against the younger champion.

Boxing writer Richie Giachetti said: "Larry didn't want to fight Ali. He knew Ali had nothing left; he knew it would be a horror."

It was around this time that Ali started struggling with vocal stutters and trembling hands.

Ali's trainer Angelo Dundee finally stopped the fight in the 11th round, the only fight Ali lost by knockout. The Holmes fight is said to have contributed to Ali's Parkinson's Syndrome.

Despite pleas to definitively retire, Ali fought one last time, on December 11, 1981 in Nassau against Trevor Berbick, losing a 10-round decision.

Ali announced that he had Parkinson's disease in 1984, a degenerative neurological condition, but continued to have a high-public profile and famously carried the Olympic torch and ignited the cauldron to signal the beginning of the Olympics in Atlanta in 1996.

He was also given a second gold medal, to replace the one he tossed in the river 36 years earlier and, in 2005, Ali received the Presidential Medal of Freedom from President George W Bush.

Ali would get married for a third time in 1986 to Veronica Porsche, who had been one of the four poster girls who had promoted the Rumble in the Jungle in Zaire.

However, they would divorce the same year.

Ali, who has nine children including Laila Ali, a boxer in her own right, married his fourth wife, Yolanda Williams also in 1986.

Despite the progression of his disease, Ali remained active in public life and was on hand to celebrate the inauguration of the first African-American president in January 2009, when Barack Obama was sworn into office.

IN HIS OWN WORDS

“Why should they ask me to put on a uniform and go 10,000 miles from home and drop bombs and bullets on brown people in Vietnam while so-called Negro people in Louisville are treated like dogs and denied simple human rights?”

February, 17, 1966 – on refusing the draft to fight in the Vietnam war.

“I’ve done my celebrating already. I said a prayer to Allah.”

June 28, 1971 –

on being told his conviction for draft evasion was overturned by the US Supreme Court.

“I told you all, all of my critics, that I was the greatest of all time ... Never make me the underdog until I’m about 50.”

October 1, 1974, after knocking out George Foreman.

“I saw your wife. You’re not as dumb as you look.”

To President Ferdinand Marcos of the Philippines a few days before he beat Joe Frazier in the Thrilla in Manila on October 1, 1975.

“What I suffered physically was worth what I’ve accomplished in life. A man who is not courageous enough to take risks will never accomplish anything in life.”

At a news conference in Houston in 1984.

“Why are all the angels white? Why ain’t there no black angels?”

Ali at a church in 1983.

“Cassius Clay is a slave name. I didn’t choose it and I don’t want it. I am Muhammad Ali, a free name - it means beloved of God, and I insist people use it when people speak to me and of me.”

After changing his name soon after the first fight with Liston in 1964

“Get up sucker and fight. Get up and fight.”

Ali taunts Liston during their second fight in 1965

“What’s my name, fool? What’s my name?”

Ali taunts Ernie Terrell, who had refused to acknowledge Ali’s change of name before their bout in 1967