The 1984 World Championship That Ended Without a Winner
The first Karpov-Kasparov World Championship match, played in Moscow starting in September 1984, ran for five months and 48 games, the longest championship match in chess history, before FIDE President Florencio Campomanes terminated it entirely on February 15, 1985, declaring no winner. Karpov led 5-3 at the time, but Kasparov had just won Games 47 and 48 in a row and was visibly gaining momentum. A rematch, covered in full in our piece on the 1985 title match, started fresh seven months later.
A match with no end in sight
Under the format in place at the time, the match would continue until one player reached six wins, with unlimited draws and games. After five months, Karpov led 5-3, but an extraordinary 40 of the 48 games played had been drawn, and both players were visibly wearing down physically, Karpov in particular had lost a striking amount of weight over the course of the match.
The last two games before it stopped
Kasparov won Game 47 as Black with a relentless passed d-pawn deciding the game in the final moves, then won Game 48 in a Petroff Defence, the exact moment Campomanes chose to end the match. A player who has just won two straight games and is building visible momentum is, by definition, not the player most people would expect a neutral official to rescue from continuing.
The official reason, and the doubts around it
Campomanes cited both players' health as the reason for termination at his press conference. Both Karpov and Kasparov have since claimed, at different points, that it was the other side pushing for the match to be cancelled, and declassified accounts have suggested Soviet officials pressured Campomanes specifically to prevent a Karpov defeat, though this remains contested rather than definitively proven.
Why "no winner" was itself the controversial part
Ending a match for player welfare is defensible on its own terms; declaring no result at all, rather than awarding the match to the player leading on games won, or structuring some other resolution, is the decision that actually drew the lasting outrage. Kasparov's furious public protest at the time set the tone for a rivalry that would run through four more matches over the next six years.
What came next
Rather than resuming the terminated match, FIDE started an entirely fresh title match in September 1985, best-of-24 games this time, a format explicitly designed to prevent a repeat of the marathon that had just ended. Kasparov won it to become the youngest World Champion in history, the subject of our companion piece linked above.