I remember watching the fights between Gene Fullmer and Carmen Basilio. They were brawls, to put it mildly.
Fullmer defeated Sugar Ray for the title, then lost it back in a rematch. After the National Boxing Association striped Robinson of the title, Fullmer and Carmine Basilio fought for the vacant crown and Gene won. He finally lost the crown to Dick Tiger.
In contrast today's boxing, there was only one undisputed championship in each weight class back then.
Not exactly true. The National Boxing Assoc. was often in conflict with the New York State Athletic Commission. The state of Nevada often sided with the NYSAC. When the NBA striped Sugar Ray, he was still recognized by the NYSAC and lost that crown to Paul Pender.
Fullmer fought Robinson 4 times.
In January 1957, he defeated Robinson by unanimous decision to win the World Middleweight title.
In May of the same year, he lost the title back to Robinson via a 5th round KO.
Robinson then lost and regained the title in bouts with Carmen Basilio.
The NBA (now WBA) stripped Robinson of the title because he hadn’t defended it. The New York State Athletic Commission continued to recognize Robinson. Robinson subsequently lost the NYSAC version to Paul Pender.
The NBA then had Fullmer and Basilio fight for the vacant title. Fullmer won via TKO in round 14.
In 1960, Fullmer defended the NBA version of the title against Robinson and they fought to a 15 round draw.
In 1961, Fullmer defeated Robinson via unanimous decision in their final fight.
In December 1960, Fullmer defended the NBA (now WBA) portion of the title