(1) Petrosian,Tigran V - Kortschnoi,Viktor Lvovich [A31]
Candidates Tournament Curacao (23), 16.06.1962

1.c4 c5 2.Nf3 Nf6
A position with numerous possibilities to transpose to a wide range of openings if White now plays 3. Nc3 or 3. g3. However, White instead chooses a direct move with immediate central action.

3.d4 cxd4
[3...e6 is also feasible when a Modern Benoni may arise if White plays d5 , or a Tarrasch Defence if Black plays that move.]

4.Nxd4 g6 5.Nc3 d5
A line that Korchnoi had played previously and is currently chosen by several players around 2700 elo or above. Instead [5...Bg7 would allow White to play 6.e4 when the Maroczy bind variation of the Accelerated Sicilian Dragon can arise after 6...d6 7.Be2 Nc6 ]

6.Bg5 dxc4
[If 6...Ne4!? 7.Nxe4 dxe4 8.Nb5 is good for White as played, for example, in Speelman-Alburt, Match London 1986. (Instead 8.Qa4+ leads to the win of a pawn but an unclear game with fair compensation for Black after 8...Bd7 9.Qc2 Nc6! 10.Qxe4 Bg7 11.Nxc6 Bxc6 Taimanov) ]

7.e3 Qa5?!
As far as can be determined this is the only game traceable in which this provocative move has been tried. Usually [7...Bg7 is chosen when play may go 8.Bxc4 0-0 9.0-0 a6 10.Qe2 (10.a4 was an earlier game restricting Black's queens-side expansionas in Smyslov-Kortschnoi, 20th URS-ch 1952.; whilst 10.Be2 has featured in more recent high level games such as Foisor-Davies, Saint John Open 1988 and Ponomariov-Nepomniachtchi, World Cup ACP, Riga 2013.) 10...b5 11.Bb3 Bb7 12.Rfd1 Qa5 13.e4 Nbd7 14.Ne6?! fxe6 15.Bxe6+ Kh8 16.Bxd7 b4 Simagin-Kortschnoi, URS-ch 23 Leningrad 1956.]

Instantly safeguarding the knight on d4 which cannot now be dislodged by e5, whilst also downgrading Black's pawn structure.

8...exf6 9.Bxc4 Bb4 10.Rc1
[Its interesting to note White prevents any break-up of his own pawn structure. This would occur after, for instance, 10.Qb3 Bxc3+ 11.bxc3 0-0 when Black is a lot better off than in the main game.]

Although preventing a knight occupying b5 in reality Black has no time for this and should immediately evacuate his king from the centre with 10...0-0.

11.0-0 Nd7
Leaving the king in the centre is really pushing Black's luck but in fact [11...0-0 now leads to serious problems for Black after 12.Nd5 and f6 is simply not defensible, for example, if 12...Kg7 (or 12...Nd7 13.Nb3 Qa4 14.a3 wins a piece.) 13.Nb3 Qa4 14.Nb6 wins outright.; So best seems to be 11...Bxc3 12.Rxc3 0-0 with some hope although White is far better.]

Continuing in positional manner by pushing back, or forcing the exchange, of one of Black's few developed pieces. However, possibly neither player realised just how bad Black's position was at this stage in the game. After only 12 moves, in a World Championship Candidates game between a soon to be World Champion, and a later World Champion finalist, Black is in fact already lost! [12.Bxf7+ is already playable although the variations are not so easy to visualise. White gets a surprisingly strong attack for the piece sacrifice as the Black king wanders the board and his remaining forces are immobile. Some possibilities are: 12...Kxf7 13.Qb3+ Ke8 (13...Kg7 14.Nd5 Bd2 15.Ne6+ Kf7 (15...Kh6 16.e4 Bxc1 17.Qh3# ) 16.Ndc7 Rb8 17.Ng5+ Kg7 18.Nce6+ Kh6 19.Nf7+ Kh5 20.Ng7+ Kg4 21.Qc4# ; 13...Kf8 14.Ne6+ Kf7 15.Ne4 Re8 16.N6g5+ Ke7 17.Qe6+ Kf8 18.Qf7# ) 14.Qe6+ Kd8 15.Nd5 Re8 16.Qf7 and the threats of Ne6 or Rfd1 mean Black's centrally placed king does not survive.]

[12...Bxc3 was once again the best hope although after 13.Rxc3 0-0 14.b4 Qd8 15.Qc1 White is very much in charge.]

13.b4! Qe5
[Other queen moves are no better eg 13...Qd8 14.Bxf7+! Kxf7 15.Qb3+ Ke8 16.Nd5 Bd6 17.Ne6 and the Black queen is trapped.; 13...Qxa3 leads the queen up a blind alley and again becomes trapped after 14.Nd5 Bxb4 15.Ra1 Qb2 16.Ra2 ; Whilst offering an exchange of queen by 13...Qh5 14.Qxh5 gxh5 fails to reduce the pressure much after 15.Nd5 Bd8 16.Be2 h4 17.Bg4 and Black barely has any decent moves, for instance, if 17...0-0 18.Rxc8 wins instantly.]

14.f4! Qb8
[If Black accepts the pawn offer then too many lines are opened: 14...Qxe3+ 15.Kh1 and to avoid the queen being lost by Rf3 or material being lost by Re1 and Nd5, Black must play 15...Nb6 but then 16.Nd5 wins easily 16...Nxd5 17.Bxd5 Qxa3 18.Rc7 as Re1 follows.]

Black is not given a second chance and is swept away after this classic sacrifice.

15...Kxf7 16.Qb3+ Ke8
[16...Kg7 17.Ne6+ Kh6 18.Rf3 g5 19.f5 g4 20.Qc4 and mate cannot be prevented.; 16...Kf8 is similar to the lines given earlier and Black soon perishes following 17.Ne6+ Kf7 (and also 17...Ke8 18.Nd5 Bd6 19.Ndc7+ Bxc7 20.Nxc7+ Kd8 21.Rfd1 ) 18.Ng5+ Kg7 19.Qf7+ Kh6 20.Ne6 ]

17.Nd5 Bd6 18.Ne6 b5 19.Ndc7+ Ke7
At first sight White has over-reached. However, White's next brilliantly shows this is not the case.

20.Nd4! Kf8
[20...Bxc7 21.Nc6+ wins the queen and Black gets insufficient material for it after 21...Kf8 22.Nxb8 Bxb8 due to 23.Rxc8+ ; On the other hand Black gets enough material for the queen with 20...Qxc7 21.Rxc7 Bxc7 but not for long as the open king and uncoordinated pieces are telling factors after 22.Qe6+ Kf8 23.Qc6 Ra7 24.Ne6++- ]

[After 21.Nxa8 Black resigned as he will remain a piece down since the Na8 cannot be captured or trapped eg 21...Qxa8 (21...Bb7 22.Qe6 Bxa8 23.Qxd7+- ) 22.Qe6 Be7 (22...Qb8 23.Nc6 Qc7 24.Ne7+- ) 23.Nc6+- ] 1-0