Since 2018, most of the games of chess I’ve analysed seriously have been engine games. I’ve therefore developed a somewhat atypical frame of reference for recognising themes and patterns. I’m more likely to say “Oh I saw that in Alliestein-Komodo” than “Carlsen played like this against Aronian” And that turned out to be the case once again when I saw a really nice exchange sacrifice during the ongoing TCEC Superfinal between Stockfish and Leela.
Let’s start with the game it reminded me first of all, and that was Stockfish-rofChade from Season 18 of TCEC Division P (https://tcec-chess.com/#div=p&game=121&season=18) That was back in 2020 when Stockfish was still “Classical” (instead of NNUE) and then fresh-faced TCEC chatters like mrbdzz were still dreaming of an era of Leela dominance! Avid readers of “The Silicon Road to Chess Improvement” (are there any other kind?) should recognise this position:
Game: Stockfish-rofChade TCEC Season 18 Division P after 19…Bf5
Poor rofChade had been given a slightly ropey Modern to deal with and Stockfish had played originally with kingside castling combined with a sharp g4-g5 push. What Stockfish did now was perhaps not very surprising, but it was quite strange to witness.
20.b4 Qd8 21.Nxb5
Game: Stockfish-rofChade TCEC Season 18 Division P after 21.Nxb5
Stockfish achieves an overwhelming advantage on the queenside which “forces” Black to grab the exchange on a1 to redress the material balance in his favour as compensation.
21…Bxa1 22.Rxa1
Game: Stockfish-rofChade TCEC Season 18 Division P after 22.Rxa1
So Black has got his material but now his kingside – lacking the protection of the dark-squared bishop – is greatly weakened and Stockfish turned its attention towards it!
22…Qc8 23. c4 a6 24. Nd4 Nd7 25. Nxf5 gxf5 26. Bd4+ f6 27. f4 Rg8 28. Kf2 Rg7 29. Ne6 Rg8 30. Qe3 a5 31. b5 Ndf8 32. Ng5 Rg7 33. Bd3 Qd7 34. Qh3
Game: Stockfish-rofChade TCEC Season 18 Division P after 34.Qh3
with a crushing position. The game struck me because it seemed that Stockfish had forced Black to weaken its kingside by taking action on the queenside! You can understand why I put this into the chapter called “Whole Board Play”
So let’s turn now to the game that lit this lightbulb in my head! Game 30 of the ongoing TCEC Superfinal between Stockfish and Leela (https://tcec-chess.com/#div=sf&game=24&season=28) I liked the opening exit a lot – well done Jeroen – which was a fairly normal Schmid Benoni offering the engines plenty of scope to display their own specific brand of genius!
Game: Stockfish-Leela TCEC Season 28 SuperFinal. End of book exit after 10…Nd7
Black’s last move prevents a quick e4-e5 from White (which might prove irritating with the bishop on f4 pointing towards the rook on b8). Black’s only source of counterplay involves queenside expansion with …a6 and …b5. White has a variety of ways of dealing with that but it’s not easy to choose between them. There are 2 main approaches:
- White can exchange off the dark-squared bishops with 11.Qd2 and Bh6 and then meet …a6 and …b5 with the blocking axb5 …axb5, b4. This sophisticated plan has been the overwhelming choice of human players.
- White can meet 12…a6 with 12.a5 and stop Black from setting up a pawn roller on the queenside. This seems extremely natural but White has to work out on the 12th move how to prepare for Black’s resulting pressure along the b-file (starting with b2) after …b5, axb6 …Rxb6. A couple of games have been played with this plan, but have given decent results for Black.
The sophisticated human plan is also Torch’s favourite line. It gives White an appreciable advantage though not enough to force a win against Stockfish!
11. Qd2 a6 12. Bh6 b5 13. axb5 axb5 14. Bxg7 Kxg7 15. b4
Line: after 15.b4
This position has led to 7 wins and 1 draw for the white pieces in over-the-board games, although in fairness the white players have tended to be around 200 ELO higher.
15…cxb4
The most common human reply
16. Na2
Line: after 16.Na2
The knight is heading for b4 and then c6!
16…Nc5
A Stockfish novelty: 16…Nf6 has been most common until now
16… Nf6 17. Nxb4 Bd7 18. e5 dxe5 19. Nxe5 Ra8 20. Bf3 Rxa1 21. Rxa1 Bf5 22. g4 Bc8 23. Ra7 Qd6 24. Qc3 Na6 25. Nxa6 Bxa6 26. g5 1-0 Tempone,M (2450)-Pla,S (2235) Buenos Aires BCA op 1988
The text (of course) leads to some intricate tactical play to hold Black’s position together!
17. Nxb4 Bb7 18. Qd4+ e5
Line: after 18…e5
A shocking defence that seems to blunder a pawn in 2 separate ways!
19. Nxe5
19.dxe6+ f6 simply absorbs the pressure and intends …N7xe6 to recapture the e6-pawn after which the e4-pawn is under pressure from the knight on c5 and the newly-freed bishop on b7. Torch prefers to keep the a8-h1 diagonal closed.
19…Qf6
19…dxe5 20.Qxc5
20. f4 Rfe8
Line: after 20…Rfe8
You can imagine a human player might struggle to keep everything together as White! The complications lead to a somewhat better position for White but one that Stockfish has no trouble holding:
21. Bd3 Nxe4 22. Qxe4 dxe5 23. fxe5 Qxe5 24. Qxe5+ Rxe5 25. Ra7 Rg5 26. Rf2 Nxd5 27. Na6 Bxa6 28. Rfxf7+ Kg8 29. Rg7+ Kh8 30. Rxh7+ Kg8 31. Rhg7+ Kh8 32. Rgf7 Bb7 33. h4 Rh5 34. Raxb7 Rxb7 35. Rxb7 Rxh4 36. Rxb5 Nf4
Line: after 36…Nf4
Stockfish’s solution in the game was quite special. Note that even on my much less powerful hardware, the TCEC continuation is the only one that Stockfish considers.
11.Qd2 a6 12.a5
Game: after 12.a5
Restraining …b5 so Black uses the break to open the file and develop pressure against b2 with his rook on the b-file.
12…b5 13.axb6 Rxb6
Game: after 13…Rxb6
The tame 14.Ra2 and 14.Na4 have been tried by (pretty strong) white players. The engines still like White but they don’t have much of a problem holding Black’s position in engine games. In particular I liked the engines’ dynamic response against 14.Ra2 (tried by the very strong Alexander Moiseenko in 2000): 14…f5
Line: after 14.Ra2 f5
Back to the game however, Stockfish‘s choice (a novelty) initially looks like the blunder of a weak player!
14.b3
Leela plays 14…Nb5
Game: after 14…Nb5
Suddenly it looks as if White has been very careless with Black’s pressure on the h8-a1 diagonal and is now going to have to lose material. I think Stockfish had anticipated that however 😉
15.Na4 Bxa1 16.Rxa1
Game: after 16.Rxa1
That’s it simply: Stockfish is sacrificing the exchange and it considers that White already has a decisive advantage of +1.54! (in fairness, I have to point out that this eval decreased to 0.67 on move 19 before jumping to 2.23 on move 24) Leela was pessimistic all the way through.
(In case you’re wondering, Black could have refused the exchange with 15…Rb7 as Torch did in many of my engine games. However, in that case White simply plays 16.Rad1 (or 16.Rae1)
Line: after 16.Rad1
after which all of Black’s hopeful pressure along the h8=-a1 diagonal and b-file has been neutralised leaving Black with little to show for the space disadvantage. Hardly lost for Black, but Black’s opening has simply not been a success.)
Back to the game, after 16…Rb7 there arein fact 2 approaches. In the game, Stockfish powered through in the centre with 17. e5
Game: after 17.e5
Looking back to the example that started this article, we can say that by daring Black out on the queenside – “take my rook or admit that you’ve achieved nothing” – Stockfish has weakened Black’s control of his centre which was exploited powerfully:
17…Qc7 18. Qe3 Nd4 19. exd6 Nxf3+ 20. Qxf3 exd6 21. Qg3 Ne5 22. Bxe5 dxe5 23. Qe3 Rb8 24. Nxc5 Rd8 25. Bc4 Rb6 26. Rd1
Game: after 26.Rd1
3.40 from Stockfish!! Black’s fundamental problem is an inability to get any grip on the weakness of its dark squares. Ne4 and d6 is coming which will force Black to give back the exchange. And Stockfish wouldn’t be Stockfish if it hadn’t calculated that the aftermath is painful too!
26…h5 27. Ne4 Bf5 28. d6 Rbxd6 29. Rxd6 Rxd6 30. Nxd6 Qxd6 31. Qa7 Qf6 32. c3 e4 33. Qxa6 Qxc3 34. Qa7 Be6 35. Qa8+ Kh7 36. Qxe4 Bxc4 37. bxc4
Game: after 37.bxc4
And Stockfish won this queen ending without breaking a sweat.
Interestingly, there was another approach apart from 17.e5 which Stockfish tried in one of my engine games: simply 17.Nb2
Line: after 17.Nb2
This turns out to be even closer to the introductory example: Stockfish’s actions on the queenside “force” Black to give up the dark-squared bishop which allows Stockfish to build up pressure on the kingside. Whole-board play! One of my engine games Stockfish-Torch continued
17…Re8 18. Nc4 f6 19. Na5 Rb6 20. Bh6 Kh8 21. Nc4 Rb8 22. Na5 Na7 23. h4
Line: after 23.h4
23…Rb4 24. Bd3 Rb8 25. c3 e5 26. Qe3 Rg8 27. Nd2 g5 28. Nf3 gxh4 29. Nxh4 Nf8 30. Be2 Ng6 31. Nxg6+ Rxg6 32. Bh5 Rg8 33. f4
Line: after 33.f4
33…Bd7 34. f5 Be8 35. Bd1 Ra8 36. Qh3 Rc8 37. Kh1 Qe7 38. Kh2 Nb5 39. Be2 Rb8 40. g4 Bd7 41. Rg1 Rbf8 42. Nc6 Qf7 43. Rg3 c4 44. Bxc4 Rg7 45. Qh4 Rfg8 46. Be2 Nc7 47. Bxg7+ Qxg7 48. c4 h6 49. b4 Ra8 50. Kg2 Kg8 51. Kf2 Kh7 52. Ra3 Be8 53. Qg3 Qg5 54. Qe3 Qg7 55. Qc1 Bd7 56. b5 Ne8 57. b6 Bc8 58. Na5 Rb8 59. Rb3 Qd7 60. Nc6 Ra8 61. Na5 Rb8 62. Rh3 Qg7 63. Qe3 Qf8 64. Bd1 Bd7 65. Nc6 Rb7 66. Nd8 Rb8 67. Nf7 Kg7 68. Nxh6 Qe7 69. g5 fxg5 70. Ng4 Rxb6 71. Qxb6 Bxf5 72. exf5 Qd7 73. Kg2 Qe7 74. Qb8 Qd7 75. f6+ 1-0
I hope you enjoyed that example! There truly is so much amazing strategical play to admire in the top engine games!