Last year, it was Korchnoi's complaint: this year, it's beginning to look like Korchnoi's revenge. Victor Korchnoi, formerly of the Soviet Union, rated the world's second-strongest active chess player, asked for political asylum in the Netherlands last July, complaining about the treatment he has been receiving from the Soviet [WORD ILLEGIBLE] bureaucracy.

After his walkout, that same bureaucracy tried to have him excluded from the world championship quarter finals, But he won his right to play and now, after 12 bitterly contested games in Italy, he has eliminated Tigran Petrosian, one of the Soviet Union's best hopes for an all-Russian championship match next year. Later this year, in the championship candidates' semifinals, he will meet another Russian hopeful, Lev Polugaevsky, and the chances are good that next year he may play for the championship against Anatoly Karpov, who beat him by only one point in their last match three years ago .

Korchnoi's close victory over Petrosian (and the bureaucracy) was the highlight in the four quarterfinal matches that took place simultaneously in Italy, Switzerland, the Netherlands and Iceland during the past two months. Meanwhile, in Lucerne, Polugaevsky squeezed out a one-point victory over Henrique Mecking of Brazil in a match that saw both players cabling home for help in analyzing tricky adjourned positions. In Rotterdam, Lajos Portisch of Hungar scored the most decisive victory of the quarterfinals, beating Bent Larsen of Denmark by three points. And in Reykjavik, scene of his 1972 loss to Bobby Fischer, former champion Boris Spassky fought to a 6-6 tie with Vlastimil Hort of Czechoslovakia and then was stricken with appendicitis. It may be a month or more before Spassky and Hort can sit down to a playoff, and unti then Portisch can only wonder who will be his opponent in the semifinals.

In all the matches except Portisch-Larsen, the margin was (or will be) a single point, illustrating how closely matched the world's top grandmasters are today. And the relatively lopsided Portisch-Larsen score (6 1/2 to 3 1/2) does not give an accurate idea of how well the two players were matched. Many of their 12 games were grueling battles in 70 or 80 moves, sometimes ending in draws or in victory by the smallest possible margin.

In this position from their third game, for example, Larsen's winning chance lies basically in the fact that he is able to move his king over to the queenside.

Some of the games that ended up as draws were among the hardest-fought of the quarterfinals - for example, the struggle in the first Mecking-Polugaevsky game, a contest bristling with fine tactical points. It might be counted as a moral victory for the young Brazilian player, who made a remarkable comeback from an apparently hopeless position.

The see-saw course of the game below typifies the close balance of the Spassky-Hort match. Black's combination on the 22nd move seizes the initiative and destroys white's pawn structure. This would be decisive against most opponents, but Spassky's lightning counterattack quickly turns the tables. Hort lost, technically, because the time ran out on his clock, but spassky clearly had a decisive advantage despite his opponent's material superiority; once the white king gets to his KN6, thretening a mating attack as well as the capture of black's unprotected KRP, the game is strategically over.