Heavyweight unification series Heavyweight unification series The heavyweight unification series, also known as the Heavyweight World Series, was a sequence of professional boxing matches held in 1986 and 1987 to crown an undisputed champion of the heavyweight class. The series was produced by HBO Sports and promoted by Don King. It ended with Mike Tyson as undisputed champion, holding the championship belts of the International Boxing Federation, World Boxing Association, and World Boxing Council. Prior to the series, the last undisputed heavyweight champion had been Leon Spinks, who won the championship in his 1978 victory over Muhammad Ali. Spinks had been stripped of
Undisputed champion recognised a different champion. The disputes were usually short-lived as a lucrative fight would be organised between the rival champions. The longest split was ten years, of the middleweight title, between Mickey Walker's move up to heavyweight in 1931 and NBA champion Tony Zale's defeat of NYSAC contender Georgie Abrams in 1941. An early use of "undisputed" appears in a "New York Times" preview of the 1941 fight. The growing popularity of boxing outside of the USA led to creation of various boxing organizations, each strengthening their influence (most notably BBBofC) and having their own champion. This resulted in a