Crossover boxing maybe commonplace in boxing's modern era, but it is something which also occured before the turn of the millennium.
One example being in 1976 when Japanese wrestling star Antonio Inoki faced the undisputed world heavyweight champion Muhammad Ali in Japan.
In a fight billed as 'The War of the Worlds', Inoki wanted to prove that wrestling was the premier combat discipline and a win against boxing's biggest name would go a long way in cementing that claim.
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When was the Inoki vs. Ali fight?
The fight took place on June 26, 1976.
Where was the Inoki vs. Ali fight?
The fight was staged at Nippon Budokan in Tokyo, Japan, 14,500 fans were in attendance.
What happened in the Inoki vs. Ali fight?
Antonio Inoki came flying out the blocks in round one, sliding at the legs of Muhammad Ali who sidestepped the attack. This was allowed under the special rules created for the contest.
Throughout the first seven rounds Inoki targeted Ali's legs in an attempt to get the world heavyweight champion on the canvas, but the American was able to dodge these efforts effectively.
The first knockdown of the contest was scored by Inoki in round seven who after being caught with a long jab, sent Ali down with a sweeping kick.
Inoki knocked Ali down a second time in round eight with two more kicks, but the referee did have to warn the Japanese wrestler about a low blow.
The fight then followed a similar pattern to the start with Inoki trying to chop Ali down who was finding success with his own punches that he was throwing.
After 15 rounds, both men shaked hands following the conclusion of this entertaining contest.
Was Inoki vs. Ali a real fight or staged?
When Muhammad Ali signed the contract for this fight with Antonio Inoki, the undisputed world heavyweight champion was under the impression that it would be an exhibition bout instead of a real contest.
However, when Ali watched Inoki train six days before, the Japanese wrestler was practicing drop-kicks and violent grapples, giving the impression that the upcoming fight was legitimate.
Inoki alleges that he was asked the following by Ali at the time, "OK, so when do we do the rehearsal?".
"No, no. This isn't an exhibition. It's a real fight!", Inoki responded.
Ali's representatives then began to renegotiate the rules. It was decided that Inoki would not be allowed to throw, grapple or tackle Ali, and no kicks could be landed unless one knee was on the canvas. Ali's camp also demanded that the rules could not be made public before the fight.
These newly created rules meant that Inoki spent the majority of the 15 rounds moving around like a crab as he looked to land his brutal leg kicks on Ali.