TCEC Season 17 League 2 Game 29 – Pirarucu-RubiChess
|Game||Season 17, League 2, Game 29|
|Links|| TCEC archive|
|Position after 25. b4|
1. e4 c6 2. d4 d5 3. e5 Bf5 4. Nc3 e6 5. g4 Bg6 6. Nge2 c5
End of book into Caro-Kann defense, advance variation, van der Wiel attack. By Lichess masters database, the book exit position is reasonably sharp with good winning chances for both sides, including a reasonable number of top level GM games.
7. h4 h5 8. Nf4 Bh7 9. g5
Here was the first significant choice what comes to the pawn structure. The move played is the second most popular move here, and the move preferred by Stockfish 11. The top masters move and the top Leela move (T42810 / 1M nodes) was to take the h-pawn with the knight, instead, with 9. Nxh5.
9... cxd4 10. Nb5 Be4 11. f3 Bf5 12. Nxd4 Ne7 13. Nxf5 Nxf5 14. Bd3 Qa5+(N)
Novelty by the Lichess masters database. Both Stockfish and Leela consider this a slight inaccuracy. The main book moves and the top Stockfish and Leela moves were 14... g6 and 14... Qc7.
15. c3 g6 16. Bxf5 gxf5 17. Kf2 Nc6 18. Nd3 O-O-O 19. f4 Kb8 20. Qe2 Qa6 21. b3 Ba3 22. Bd2 Rc8 23. Kg3
Leela suggests here an interesting alternative: 23. Rhb1 Rc7 24. b4 Qc4 25. Rb3 Nd4 26. cxd4 Qxd4+ 27. Be3 Qxa1 28. Rxa3. White has two pieces for a rook and a pawn, and both sides have strong attacking ideas: white with the queenside attack against the king, and black penetrating with the rooks via the open c-file to exploit the open king.
23... Ne7 24. Qf3
The queen move prepares for the b-pawn push. The point here being that white now has a reply to black's d4 move with c4 and Nc5 with an exposure attack to the bishop on a3. Example lines:
- 24. b4 d4 and white now has to take with 25. cxd4 and white's queenside collapses. Here, after 25. c4, black would simply play 25... Rxc4.
- 24. Qf3 Rc7 25. b4 d4 26. c4 Rxc4 27. Nc5 and here black has to give up the exchange with 27... Rxc5 to save the bishop on a3.
In the game, black encourages white a bit more to push the b-pawn, by eliminating the option to play Nd5 after black's d-pawn push.
24... Ng6 25. b4 (diagram)
The b-pawn push now is interesting. At the first glance, the pawn move seems to trap the black bishop, but there does not seem to be a way for white to attack and win it due to black's counter-threats as seen shortly. Black could have moved the bishop earlier to safety, but with this pawn structure, the bishop would not have many squares to play with. Further, the bishop on a3 plays a role to stop white pushing the queenside pawns.
|Position after 41... Kc5|
25... Qa4 26. Rh2 a5 27. Rb1 Qc2 28. Rb3 Qxa2 29. Qd1 a4 30. Rb1 Qc4 31. Qf3 Qa2 32. Qf1 d4 33. Nc5
Interestingly, even the more direct attack would not win the trapped bishop: 33. Be3 Qc4 34. Bxd4 Rhd8. The black bishop is trapped, but white has no direct way to attack it. Some examples:
- 35. Ra1 Bxb4 36. cxb4?? Rxd4
- 35. Nc5 Qxf1 36. Rxf1 Bxb4 and white bishop would be hanging after 37. cxb4??
- 35. Qf3 Ne7 36. Nc5 Rc7 and the bishop cannot move away to prepare Ra1, as 37. Bg1?? Rxc5 38. Bxc5 Rd3 and the queen is pinned.
33... Bb2 34. Be3 Rxc5
A key move for black, sacrificing an exchange to create a strong passed pawn. Now both sides must play precisely as both sides have deadly threats if given free tempi.
35. bxc5 dxc3 36. c6 Ne7 37. cxb7 Nd5
Another key move for black, requiring white to go for perpetual checks. The black pawns are too advanced and white's king is too exposed.
The alternative with 37... Qb3 38. Qa6 Qxb7 39. Qxa4 would be losing for black with exchange down and open king.
38. Qa6 Nxe3 39. Qa8+ Kc7 40. Qa7
Note that white could have also grabbed material with 40. Qxh8. The queening threat with check would require black to take the b-pawn with 40... Kxb7 and white would be just in time for perpetual checks: 41. Qe8 Qxb1 42. Qb5+
39... Kc7 40. Qa7 Kc6 41. Qa6+
No time to take the knight: 41. Qxe3 Qxb1 and white's queen is misplaced.
41... Kc5 (diagram) 42. Re1
White had to continue with the perpetual checks with either Qa7+, Qa5+, or Qd6+. The easiest plan was 42. Qd6+ Kc4 43. Qa6+ Kc5 and repeat with 44. Qc6+. Black could not have escaped the checks, as:
- 42. Qd6+ Kb5?? 43. Rhxb2+ cxb2 44. Rxb2+ Qxb2 45. b8=Q+ Rxb8 46. Qxb8+ Ka5 47. Qxb2 wins the queen.
- 42. Qd6+ Kc4 43. Qa6+ Kd4 44. Re1 threatening Qa7+ to win the knight 44... Nd5 45. Rd1+ Kc5 46. Qd6+ Kb5 47. b8=Q+ Rxb8 48. Qxb8+ Ka6. The position might still be a draw, but white has a strong initiative.
The move played allows black to escape the perpetuals and start pushing the queenside pawns.
|Position after 53... Kd4|
42... Nd5 43. Qd6+ Kc4 44. Qc6+ Kb4 45. Qd6+ Ka5 46. Qc5+ Ka6
White ran out of checks. Now white will win a rook and be two exchanges up, but the two black passed pawns are strong.
47. Qc8 Qb3 48. b8=Q+ Rxc8 49. Qxc8+ Ka5 50. Qa8+ Kb5 51. Qe8+ Kb6 52. Qb8+ Kc5 53. Qc8+ Kd4 (diagram)
Again, no more checks for white. Now black can start advancing the pawns.
|Position after 69. Kxg2|
54. Rhe2 a3 55. Kh2 a2 56. Qa8 Kd3 57. Rf2 a1=R
The a-pawn wins back the first exchange.
58. Rxa1 Bxa1 59. Qxa1 Ne3 60. Kh3 c2 61. Rf3
Now white gives back another exchange for the c-pawn, transitioning into a losing king-pawn endgame.
61... Ke4 62. Rg3 Qc4
Now the threat is Qf1+ forcing the queen exchange. After that, winning the rook by the queening threat would be a simple matter for black. An example threat line: 63. Qc1 Qf1+ 64. Qxf1 Nxf1 65. Rc3 Ne3 66. Kg3 Kd4 67. Rc7 Nc4 and the rook is cut off from the c-pawn.
63. Qh1+ Kd3 64. Qf1+ Kd2 65. Rg2+ Nxg2 66. Qxc4 c1=Q 67. Qa2+ Qc2 68. Qxc2+ Kxc2 69. Kxg2 (diagram)
After the wild tactics and all pieces exchanged, black has a winning king-pawn endgame. The key weakness is white's f4 pawn, which white can only protect with king on the 3rd rank. The magic squares for the black king are c3/c4/d3/d4/e3/e4. When the black king is on any of these squares, the white king cannot get into opposition. And while the black king can play simple vertical waiting moves, the white king has to retreat giving the black king access to horizontally advancing moves.
69... Kd3 70. Kf3 Kd4 71. Ke2
Slightly more resilient was 71. Kf2 Ke4 72. Kg3 Ke3 and white cannot prevent Kxf4.
71... Ke4 72. Kd2 0-1.
Black wins by the TCEC win rule. A possible continuation: 72... Kxf4 73. Kd3 Kxe5. Two connected passed pawns in a king-pawn endgame is an easy win for black.
The blunder of 42. Re1 is an interesting move to analyze. Even with only some basic tactics skills, it should not be hard to see that white should be able to win the black rook and be two exchanges up. However, black's two pawns are quite advanced. To stop the pawns, white probably has to give back the exchanges: A very rough rule of thumb is that a rook can often be exchanged to a minor and a pawn when there are some pieces on the board, although precise tactics matter. Considering the white king position, it should not come as a surprise that black can also enforce the queen trade at some point. Summing up, black should be able to enforce a king-pawn endgame, unless white finds an active plan such as perpetual checks or other tactics to prevent it.
Then the question is that when such a king-pawn endgame is good for black. It usually makes sense to consider the pawn breaks (none available for either side) and king positions. If the kings are roughly where they are on move 42, the question is then whether black can win the all-important f4-pawn. Here, identifying the winning squares for the black king (rectangle c3-e4) is key, as it gives black a simple goal to enter the king-pawn endgame. Thus, simply by positional analysis and some tactical awareness, it is possible reason that white should have probably continued with the perpetual checks, rather than relied upon material advantage with the move played (42. Re1).
To no surprise, Leela will come to the same conclusion with a very limited search (roughly 10 nodes needed), and would rather play a perpetual check move than the one in the game (42. Re1.)
- https://lichess.org/WYty7i74#27 (accessed on 2020-01-26)