(1) Pachman,Ludek - Neikirkh,Oleg [D41]
Interzonal-04 Portoroz (13), 27.08.1958

1.c4 Nf6 2.Nc3 e6 3.Nf3 d5
By threatening d4, Black forces White's hand.

[4.e3 is the main alternative when play may go 4...Be7 5.b3 0-0 6.Bb2 with a Nimzo-Larsen Attack Opening as in Grischuk-Kramnik, Tal Memorial Blitz, Moscow 2018.]

4...c5 5.cxd5 Nxd5
Black recaptures with the knight giving the Semi-Tarrasch Defence. [The pawn recapture 5...exd5 invites a standard Tarrasch Defence with 6.g3 when Black then plays Nc6. Instead White can try and exploit the early Nf6, instead of an early Nc6, with (6.Bg5 Be7 7.dxc5 Be6 8.e3 0-0 9.Be2 Nbd7+/- Goldin-Shabalov, Philadelphia National Open 1999. (but better is 9...Bxc5 ) ) ]

Favoured by Botvinnik and other top GMs from his era. This move is a more restrained line than [6.e4 Nxc3 7.bxc3 cxd4 8.cxd4 Bb4+ which used to be thought of as promising for White, but in recent years, many of the World's elite GMs have played this line as Black.]

[6...cxd4 is a way to clarify the central pawn structure early in the game. For example, Anand-Karpov, FIDE W-ch KO 1998 continued 7.exd4 Be7 8.Bd3 Nc6 ]

7.Bc4 Nxc3
[7...cxd4 is again feasible.]

8.bxc3 Be7 9.0-0
[9.Ba3 0-0 10.0-0 Qa5 is no major problem for Black as in Wong-Lee, Honk Kong ch (qualifier) 2013.]

9...0-0 10.Qe2
[10.e4 is the other main White approach in this position when Black can obtain a reasonable game with 10...b6 although this did not prevent an incisive White win in Keres-Geller, Candidates play-off Moscow 1965.]

10...b6 11.Rd1 cxd4 12.exd4 Na5 13.Bd3 Bb7 14.Bf4 Qd5
An active placement of the queen, which is quite playable. However, in the game continuation it is eventually shown to be somewhat vulnerable on this square. [14...Rc8 is perhaps safer eg 15.Rac1 Bf6 with about level chances at this stage in the game Gipslis-Barshausaka, LAT-ch Riga 1961]

15.Rab1 Rac8
Black plays a natural move that prevents c4 for the time being but follows it up incorrectly. [15...Bc6 has also been played in this position but even though Black now covers the b5 square it doesn't quite work out. 16.Be5 (16.c4 can be played since after 16...Qh5 17.d5 gives White a space advantage in the centre as 17...exd5 loses to 18.Qxe7 ) 16...Ba4 (or 16...f6 17.c4 is again promising as in Mraz-Glaas, Eberhardt Wilhelm Cup-final B ICCF 1966.) 17.c4 forces 17...Qd7 Stahlberg-Szabo, Olympiad final Helsinki 1952. (as 17...Bxd1 loses to 18.Bxh7+ ) ; 15...Qh5 is interesting with an unclear position arising from 16.Rb5 Bxf3 17.gxf3 Qh3 ; 15...Bf6 is perhaps the most solid option continuing to pressure White's centre whilst adding support to the kings-side.]

16.Rb5 Qd8?
Thus Back has lost a tempo with the queen, hence the retreat [16...Qd7 which guards e6 and hence cuts down on White's sacrificial possibilities, is much better.]

A strong move that leaves Black with a very tricky defence due to White's many attacking options.

[Advancing pawns in front of the king allows White a torrent of sacrifical possibilities: 17...h6 18.Nxe6 (18.Nh7 is not so good as Black can sacrifice the exchange for some play after 18...Rxc3 (18...Re8 saves the rook but loses outright to 19.Qg4+- ) 19.Nxf8 Bxf8 20.Bd2 Ra3 21.Bxa5 Rxa5 22.Rxa5 bxa5 ) 18...fxe6 19.Qxe6+ Kh8 (19...Rf7 20.Bg6 Qe8 (20...Qf8 21.Rf5+- ) 21.Rdb1 Nc6 (21...Rc6 22.Bxf7+ Qxf7 23.Qxf7+ Kxf7 24.Rxa5 bxa5 25.Rxb7 Rxc3 26.h4 (and not 26.Bd6 which wins a piece but throws the game to 26...Rc1# ) 26...Kf8 27.Be5 with good winning chances as a7 will also soon fall.) 22.Re1 Nd8 23.Bxf7+ Qxf7 24.Qxe7 Qxf4 25.Rbe5 and White commands the board with a large advantage.) 20.Qg6 Kg8 21.Qh7+ Kf7 22.Bg6+ Kf6 23.Be8 Ke6 24.Re1+ mating.; 17...g6 is no better than 17...h6 18.Nxh7 Rxc3 in this line the exchange offer doesn't generate any real play. (18...Kxh7 also loses rapidly to 19.Qh5+ Kg7 20.Qh6+ Kg8 21.Rh5 gxh5 22.Qh7# ) 19.Nxf8 Bxf8 20.Bxg6+- ]

[18.Bxh7+ is too early since Black can just defend with 18...Kxh7 19.Rxg5 Qf6 (and certainly not 19...f6 20.Qh5+ Kg8 21.Rxg7+ Kxg7 22.Bh6+ Kh8 23.Bxf8+ Kg8 24.Bh6+- as White has Rd3 and Qg6+ or Qg4+.) ; 18.Rxg5 is another interesting option for White. Some possible lines are 18...g6 (18...Rxc3 grabs a pawn but reaps a whirlwind with 19.Bxh7+ Kxh7 20.Qh5+ Kg8 21.Rxg7+ Kxg7 22.Bh6+ Kg8 (or 22...Kh7 23.Bg5+ Kg7 24.Qh6+ Kg8 25.Bxd8 Rxd8 26.Qg5++- ) 23.Qg4+ Kh7 24.Qg7# ) 19.Qh5 Nc4 (19...Rxc3 is once again bad due to 20.Bxg6 fxg6 21.Rxg6+ hxg6 22.Qxg6+ Kh8 23.Be5++- ) 20.Re1 Qf6 and again Black is just about hanging on.]

18...Qd6 19.Bf6 Qf4
[The bishop is immune as 19...gxf6 soon leads to mate 20.Bxh7+ Kxh7 (or 20...Kh8 21.Qh5 Kg7 22.Qg4+ Kh8 23.Rh5 Rg8 24.Bxg8# ) 21.Rh5+ Kg7 22.Qg4# ]

[20.Bxh7+ looks good but is a disaster for White since Black can defend, then obtain a winning game, with 20...Kxh7 21.Qd3+ Be4 22.Qh3+ Kg8 (22...Kg6 is too macho as the game is just level after 23.Bg5 Bf5 ) 23.Rh5 gxf6 24.Rh8+ Kg7 25.Rh4 Bf5-+ as Black has both h6 and h7 guarded.]

[Once more Black had to offer the exchange to stay in the game after either 20...Qh4 21.Bd6 ; or 20...Qh6 21.Bd6 since if Black tries to save the rook with 21...Rfd8 he loses the queen to 22.Rh5 ]

21.f4 Qe7
[21...Qxg2+ 22.Qxg2 Bxg2 23.Kxg2 Rxc3 only gets a couple of pawns for the piece and White soon gains a winning edge with 24.Bd6 Rfc8 25.Bb4 R3c7 26.Bxa5 bxa5 27.Rxa5 ]

Very tempting but not the strongest. Instead the more accurate [22.Bxg7 Kxg7 23.Rg5+ Kh8 (23...Kh6 24.Qh5# ) and only then the second bishop sacrifice clearly wins: 24.Bxh7 Qxg5 (24...Kxh7 25.Qh5# ; 24...f5 25.Rd3 Qxh7 26.Qe5++- ) 25.fxg5 Kxh7 26.Qh5+ Kg8 27.Rd3+- as, although Black has about an equivalence in material for the queen, White can play g6 or Rh3 winning readily.]

The sacrifice must be accepted for if [22...Kh8 23.Qh5 f6 24.Bg6+ Kg8 25.Qh7# ]

23.Qh5+ Kg8 24.Bxg7 f5
The correct defence rather than [24...f6 25.Bxf6 Qxf6 26.Rg5+ Qxg5 27.Qxg5+ Kf7 28.f5+- as White is easily winning due to the exposed nature of the Black king.]

This looks very powerful but Black can, amazingly, defend successfully. [25.Bxf8 winning the exchange is the best option, for instance, 25...Rxf8 26.Qg6+ (not 26.Rd3 Rf7= ) 26...Qg7 (26...Kh8 is bad due to 27.Rd3 Rf7 28.Rh3+ Rh7 29.Rxh7+ Qxh7 30.Qxe6+- ) 27.Qxe6+ Qf7 28.Re1 with advantage to White but not yet a clear win.]

Possibly due to time pressure, or being "punch-drunk", from the numerous tactics in the proceeding moves, Black blunders terribly. The careful [25...Qh7 is still very complex but advantageous for Black 26.Qg5+ Kf7 27.Qf6+ (27.d5 gives White a few more chances in a murky position after 27...exd5 (27...Bxd5 allows White to draw by 28.Rbxd5 exd5 29.Qf6+ Kg8 (29...Ke8 is a serious error due to 30.Qe6+ Qe7 and now 31.Qxc8+ wins.) 30.Qg5+= ) 28.Rd3=/+ ) 27...Ke8 28.Qxe6+ Qe7 and Black is much better.]

Its mate next move. 1-0