An interzonal chess tournament was held in Portorož, SR Slovenia, SFR Yugoslavia, in August and September 1958. The top six finishers qualified for the Candidates Tournament.[1][2]
Before the final round, the leaders were: (1st) Tal 13; (2nd–3rd) Gligoric, Petrosian 12½ (though Petrosian had the bye in the last round); (4th) Benko 12; (5th–6th) Fischer, Bronstein 11½; (7th–10th) Olafsson, Averbakh, Szabo, Pachman 11.[2] In the final round Fischer had black against Gligoric; while Bronstein, Olafsson, Szabo and Pachman had relatively weaker opponents. Feeling he was forced to play for a win, Fischer played the risky but double-edged Goteborg variation of the Sicilian Najdorf. Later, while the Gligoric–Fischer game was in a critical position with Fischer having some advantage, Fischer saw that Bronstein was unexpectedly losing to Cardoso. So Fischer accepted a draw, qualifying for the Candidates.[3] Of the players on 11 points, only Olafsson won, joining Fischer in the last two qualifying positions.
The 1959 Candidates Tournament was held in Yugoslavia in Bled, Zagreb, and Belgrade in September and October 1959.[4] The top two players from the previous tournament, Smyslov and Keres, were seeded directly into the tournament and joined by the top six from the interzonal. Mikhail Tal won, becoming the challenger in the 1960 championship match.
The tournament was notable in that the two top finishers, Tal and Keres, scored heavily against the bottom of the field. If only scores between the top four are taken into account, the results of the top four are quite similar (Tal 5½/12, Keres 6½/12, Petrosian and Smyslov both 6/12). But Tal and Keres scored heavily against the bottom four, with Tal scoring an incredible 14½/16, including winning all four of his games against Fischer.
Future world champion Bobby Fischer was 16 years old at the time. He was the youngest Candidate in history until Magnus Carlsen qualified for the 2007 Candidates under a different system.
The best of 24 game match was held in Moscow. In the event of a 12–12 tie, Botvinnik, the title holder, would retain the Championship.
Due to Tal's less impressive results against the very top players, including his three losses to Keres in the Candidates, Botvinnik was the favourite.[5] Tal won the match decisively, however, by a margin of 4 points.
Position after 29.c4. Here Tal remarked that the move caused a forced material advantage for White, as 29...Ne7 can be met by 30.cxd5 Bxd5 (or 30...Nxd5 31.Bc4) 31.Bxe7 Qxe7 32.Qc1+ which would have been completely lost for Black.
Position 21.Ra1. Tal (Black) now sacrificed a knight with the speculative 21...Nf4!!, and won in the ensuing complications.
Game 6 is particularly famous, thanks to a speculative knight sacrifice by Tal on move 21. The audience became so excited that the game was moved to a back room due to the noise.[5]
Game 17 was a 41-move win for Tal. Tal (White) described the move 12.f4 as "memorable". He believed that the move would throw Botvinnik off and that it could only be exploited by opening the game for Tal's bishops.[6]
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Mikhail Botvinnik 
