JOE FRAZIER became the heavyweight champion while Ali was dormant appealing against his draft conviction and, after Ali's 1970 return to the ring, the two took part in three classic fights.
The first, billed as the "Fight of the Century" in New York in 1971, was a tremendous battle that showed Ali still possessed his skills. Frazier dropped him with a left hook in the last round and, even though Ali rose quickly, Frazier won the fight on a decision. It was Ali's first defeat after 31 victories.
Frazier lost the title to Foreman in January 1973 but the second Ali-Frazier bout still drew enormous attention in 1974 with a 32-year-old Ali winning a unanimous decision.
Then came the "Rumble in the Jungle" match against Foreman for the heavyweight crown in Kinshasa, Zaire, on Oct. 30, 1974. Ali had a surprise ploy - a passive "rope-a-dope" strategy in which he laid back against the ropes, essentially hiding behind his arms and inviting the larger, stronger Foreman to hit him until he was too tired to hit anymore.
It paid off in the eighth round, when Ali knocked out the weary Foreman with a left-right combination.
It was one of the brightest moments of Ali's career, confirming him as one of the greatest fighters of all time.
Muhammad Ali and Joe Frazier are shown in the midst of their title boxing match at Madison Square Garden. (Photo: Getty Images)
Ali (R) grimaces as Frazier connects with a left to the head in third round action of their non-title bout at Madison Square Garden, New York (Photo: Getty Images).
Ali defended his title three times in 1975 before meeting Frazier once more in October in the "Thrilla in Manila." The bout was fought in brutal heat and Ali won when Frazier's trainer would not allow him to go out for the final round.
On Feb. 15, 1978, a careless, lethargic Ali lost his title to little-known Leon Spinks in a 15-round decision. Seven months later, he reclaimed the title with a 15-round decision over Spinks. The victory, when Ali was four months shy of 37, came 14 years after he had won his first championship.
However, Ali, whose entourage helped him to spend several fortunes, needed money and refused to leave the sport even when it was apparent that age had sapped his talents.
He retired about a year after beating Spinks but came back in 1980 to fight former sparring mate Larry Holmes, losing a lopsided bout that was stopped after 10 rounds.
A year later, he ignored pleas to retire and lost to journeyman Trevor Berbick in the Bahamas. Then he retired for good with a record of 56 wins, including 37 knockouts, and five losses.