Victor Korchnoi roared back into fighting form for the 13th game of his match with Anatoly Karpov, launched a counterattack in the match's psychological byplay and finished yesterday's session in a winning position with Karpov's queen gone from the board.

Korchnoi, playing white, sealed his 42nd move in an envelope to be opened when play resumes today. The move seems fairly obvious -- Korchnoi will undoubtedly take Karpov's only remaining knight -- but it is doubtful that Karpov will show up to defend a hopeless position.

On the psychological front, Korchnoi showed up wearing the mirror-lens sunglasses that Karpov complained about during the 1978 match in the Philippines. At the same time, his attorney began a counterattack on the protest front, a side-battle that may become as complicated as the chess games. Karpov filed a formal protest earlier this week, claiming that Korchnoi had broken the match rules by speaking to him harshly after move 8 of game 12. The protest was upheld by a three-man jury, which did not take disciplinary action but warned Korchnoi that he faces a fine of more than $8,000 if he talks again during a game. Yesterday both men played in complete silence, but Korchnoi's lawyer filed an appeal for a reversal of the warning, claiming that it was unfair to set a fine before the offense was committed.

Meanwhile, at the chessboard, Korchnoi made his aggressive intentions clear as early as his 7th move, a daring pawn advance that drove Karpov's bishop back from an advanced position into a state of complete passivity. He had a strong initiative by move 18, and it grew stronger as he sacrificed two pawns to put Karpov off balance. On his 31st move, Karpov finally had to sacrifice his queen for a rook and bishop to avoid a quick checkmate. At the session's end, Korchnoi was busily whittling away Karpov's remaining pieces, and clearly headed for a won endgame with a queen and two pawns against a rook and four pawns.

The moves of Game 13 are given below.

White: Korchnoi; Black: Karpov. 1. c4, e6; 2. Nc3, d5; 3. d4, Be7; 4. cxd5, exd5; 5. Bf4, c6; 6. e3, Bf5; 7. g4, Be6; 8. h3, Nf6; 9. Bd3, c5; 10. Nf3, Nc6; 11. Kf1, 0-0; 12. Kg2, Rc8; 13. Rc1, Re8; 14. dxc5, Bxc5; 15. Nb5, Bf8; 16. Nfd4, Nxd4; 17. Rxc8, Qxc8; 18. exd4, Qd7; 19. Nc7, Rc8; 20. Nxe6, fxe6; 21. Re1, a6; 22. g5, Ne4; 23. Qg4, Bb4; 24. Re2, Rf8; 25. f3, Qf7; 26. Be5, Nd2; 27. a3, Nxf3; 28. g6, hxg6; 29. Bg3, Be7; 30. Rf2 Ne1 ch; 31. Kh1, Qxf2; 32. Bxf2, Nxd3; 33. Qxe6 ch, Rf7; 34. Bg3, Nxb2; 35. Qxd5, Bf6; 36. Bd6, g5; 37. Qb3, Bxd4; 38. Qe6, g6; 39. Qe8 ch, Kg7; 40. Be5 ch, Bxe5; 41. Qxe5 ch, Kh7; Game adjourned.