Thor Bjornsson knocked Eddie Hall down twice en-route to winning a points decision over his fellow strongman.
The Icelander was in trouble early on when he was given a count in the second round.
But he recovered to drop Hall in the third and sixth sessions to make sure of victory on the judges' cards.
The two rivals took to the ring six months after the fight was initially scheduled after Hall was forced to pull out with a torn biceps last September.
They did so in front of a sparse crowd with the first bell ringing after 1am in the desert.
Hall made the better start as he looked to land a one-punch KO before Bjornsson looked to control the bout with his jab.
And the Icelander finished the round stronger as he landed a big left hand from his southpaw stance.
But he was rocked in the opening stages of the second round with a knockdown called after the ropes kept Bjornsson up.
Hall was by now cut under both eyes but thought he had Bjornsson down again in but it was ruled a push.
Bjornsson was struggling to impose himself on the fight as Hall walked him down but he did land a one-two in the second half of the third round.
And he sent Hall crashing to the canvas at the end of the session with the Englishman woozy on his feet.
He recovered to continue with the fight now in the balance.
Hall landed first in the fourth round as Bjornsson struggled to capitalise on his knockdown but the taller man began to land as the round progressed.
Bjornsson was told in his corner that Hall was exhausted and he took the fight to the smaller man in the fifth round.
The bigger man was ahead going into the final session and he made sure of victory by dropping Hall again. And all three judges gave him the nod by a score of 57-54.
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"It feels amazing," said the winner. "I've been working my ass off for two years. I had such a good team around me who have supported me all the way through.
"On my behalf [the rivalry is over], understandably he seemed angry still, he lost the fight. There are a lot of feelings right now.
"If he wants a rematch I'll take one no problem. I would like to thank Eddie Hall and his team.
"He put up a hell of a battle. I'd never been dropped in training so he really can punch hard. But today I believe boxing technique won.
"I'm really enjoying this journey and if there are other opportunities I am at least open to it."
