Undisputed champion he was still described as "undisputed champion" by some reports. After Joe Calzaghe's super middleweight victory over Mikkel Kessler in November 2007, he was frequently described as "undisputed champion". Others disputed this, because although he held the WBA, WBC, and WBO belts, he vacated his IBF title in November 2006 rather than face a mandatory challenger, and immediately vacated other titles as well. The unified champion is defined as a boxer that holds at least two world championships of major sanctioning bodies (WBA, WBC, WBO or IBF) in their respective division. Around 2004, the World Boxing Association recognized three different
World Boxing Organization (as they did with several established champions in the lower weight divisions), the WBO sanctioned a fight between two relatively unknown fighters, Francesco Damiani (winner of the super heavyweight silver medal at the 1984 Summer Olympics) and Johnny DuPlooy, to determine the inaugural holder of its own heavyweight title in 1989. All other sanctioning bodies of boxing recognized the then-undefeated Mike Tyson as the undisputed heavyweight champion. Damiani, meanwhile, went on to become the first WBO heavyweight champion. At heavyweight, especially in the United States, the organization initially struggled to gain credibility as a major sanctioning body, with WBO heavyweight