Answers.Body: <p>The Bishop on b5 is lost after Kf8 due to either Qa5+ or a6/b5.  Reminiscent of a famous &quot;trap&quot; from over a hundred years ago:</p>
  <pre><code>[FEN &quot;&quot;]
  [Event &quot;St. Petersburg&quot;]
  [Site &quot;St. Petersburg  RUE&quot;]
  [Date &quot;1914.04.22&quot;]
  [EventDate &quot;1914.04.21&quot;]
  [Round &quot;2&quot;]
  [Result &quot;1/2-1/2&quot;]
  [White &quot;Alexander Alekhine&quot;]
  [Black &quot;Joseph Henry Blackburne&quot;]
  [ECO &quot;C61&quot;]
  [WhiteElo &quot;?&quot;]
  [BlackElo &quot;?&quot;]
  [PlyCount &quot;89&quot;]
  
  1. e4 e5 2. Nf3 Nc6 3. Bb5 Nd4 4. Nxd4 exd4 5. O-O g6 6. d3
  Bg7 7. f4 c6 8. Bc4 d5 9. exd5 cxd5 10. Bb5+ Kf8 11. Nd2 Qa5
  12. a4 a6 13. Nb3 Qd8 14. Bd2 axb5 15. axb5 Rxa1 16. Bb4+ Ne7
  17. Qxa1 Bf6 18. Qa7 b6 19. Re1 Be6 20. Kh1 h5 21. Bxe7+ Qxe7
  22. Qxb6 Qb4 23. Qc5+ Qxc5 24. Nxc5 Bd8 25. Nxe6+ fxe6
  26. Rxe6 Kf7 27. Rd6 Be7 28. Rxd5 Rc8 29. c4 dxc3 30. bxc3
  Rxc3 31. Kg1 Ke6 32. Re5+ Kd6 33. Re3 Rb3 34. Kf1 Rb4 35. Re4
  Rb2 36. Re3 h4 37. Re4 Bf6 38. b6 Kd5 39. Re8 Rxb6 40. Kf2 Rb3
  41. Rg8 Rxd3 42. Rxg6 Ke6 43. g4 hxg3+ 44. hxg3 Kf5 45.Rg8
  1/2-1/2
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-01-13T08:01:47.310Z
Answers.LastActivityDate: 2024-01-13T08:01:47.310Z
Answers.UserDisplayName: John Chernoff
Answers.Body: <p>The key to the position is black's strong center with pawns on d5 and c5. This gives black the chance to trap the white bishop with a6, b5, c4. Note that normally, in Sicilian positions where this trap also occurs, white having a pawn on d3 would stop this threat because of d3xc4. White doesn't have time to counter this threat because black is also threatening to win the bishop with Qa5+.</p>
  <p>Here are the different ways white can try and wriggle and how they fail.</p>
  <pre><code>[Title &quot;Why Kf8 wins a piece for two pawns&quot;]
  [fen &quot;rnbqk1nr/pp2bppp/8/1Bpp4/8/3P4/PPP1QPPP/RNB1K1NR b - - 0 1&quot;]
  
  1...Kf8 2. Bd2 {stops Qa5+} (2. c3 {stops the check and creates an escape square on c2 for the bishop if black plays a6...} Qa5 {but black's d5 pawn seals the bishop's fate. It has nowhere to go} 3. d4 {protecting the bishop with the queen} c4 {cutting off the bishops retreat and protection} 4. Na3 {one last hope. Note that if white's queen hadn't broken normal development rules and moved early then the bishop would have had a safe retreat square all along on a4} a6 (4...Bxa3?? 5. Qe8#) 5. Bxc4 {all that's left is to grab a pawn for the piece} Bxa3 6. Bd3 Bd6) a6 3. Ba4 b5 4. Bb3 c4 5. dxc4 dxc4 6. Bxc4 bxc4 7. Qxc4
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-01-13T13:26:10.530Z
Answers.LastActivityDate: 2024-01-13T13:26:10.530Z
Answers.UserDisplayName: Brian Towers
Body: <p>Was reviewing a recent game and the chess.com engine told me that this move was a miss, and that instead I should have played Kf8. I really don't understand the logic behind this. Is there some sort of threat I'm not seeing here? Why would I prevent myself from castling when I could just block the check?</p>
  <pre><code>[Title &quot;Confusing machine evaluation&quot;]
  [fen &quot;rnbqk1nr/pp2bppp/8/1Bpp4/8/3P4/PPP1QPPP/RNB1K1NR b - - 0 1&quot;]
   [Startply &quot;1&quot;]
  
  1...Bd7? (1...Kf8!)
  </code></pre>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-01-13T07:49:59.327Z
Comments.Text: Essence of an answer - after Kf8 you are threatening both Qa5+ and the [Noah's Ark trap](https://en.wikipedia.org/wiki/Ruy_Lopez,_Noah%27s_Ark_Trap) winning a piece, and white has no good response.
Comments.UserDisplayName: Ian Bush
Tags: <engines><blunder>
Title: Why was this move a miss?
ThreadText: # Why was this move a miss?
  
  (Asked by: username_0 on 2024-01-13)
  
  Was reviewing a recent game and the chess.com engine told me that this move was a miss, and that instead I should have played Kf8. I really don't understand the logic behind this. Is there some sort of threat I'm not seeing here? Why would I prevent myself from castling when I could just block the check?
  [Title "Confusing machine evaluation"]
  [fen "rnbqk1nr/pp2bppp/8/1Bpp4/8/3P4/PPP1QPPP/RNB1K1NR b - - 0 1"]
   [Startply "1"]
  
  1...Bd7? (1...Kf8!)
  
  **Tags:** engines, blunder
  
  > **Comments:**
  > **username_1**: Essence of an answer - after Kf8 you are threatening both Qa5+ and the [Noah's Ark trap](https://en.wikipedia.org/wiki/Ruy_Lopez,_Noah%27s_Ark_Trap) winning a piece, and white has no good response.  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_3 on 2024-01-13. Score: 7 | Accepted answer
  
  The key to the position is black's strong center with pawns on d5 and c5. This gives black the chance to trap the white bishop with a6, b5, c4. Note that normally, in Sicilian positions where this trap also occurs, white having a pawn on d3 would stop this threat because of d3xc4. White doesn't have time to counter this threat because black is also threatening to win the bishop with Qa5+.
  Here are the different ways white can try and wriggle and how they fail.
  [Title "Why Kf8 wins a piece for two pawns"]
  [fen "rnbqk1nr/pp2bppp/8/1Bpp4/8/3P4/PPP1QPPP/RNB1K1NR b - - 0 1"]
  
  1...Kf8 2. Bd2 {stops Qa5+} (2. c3 {stops the check and creates an escape square on c2 for the bishop if black plays a6...} Qa5 {but black's d5 pawn seals the bishop's fate. It has nowhere to go} 3. d4 {protecting the bishop with the queen} c4 {cutting off the bishops retreat and protection} 4. Na3 {one last hope. Note that if white's queen hadn't broken normal development rules and moved early then the bishop would have had a safe retreat square all along on a4} a6 (4...Bxa3?? 5. Qe8#) 5. Bxc4 {all that's left is to grab a pawn for the piece} Bxa3 6. Bd3 Bd6) a6 3. Ba4 b5 4. Bb3 c4 5. dxc4 dxc4 6. Bxc4 bxc4 7. Qxc4
  
  
  ---
  
  ### Answer by username_2 on 2024-01-13. Score: 3
  
  The Bishop on b5 is lost after Kf8 due to either Qa5+ or a6/b5.  Reminiscent of a famous "trap" from over a hundred years ago:
  [FEN ""]
  [Event "St. Petersburg"]
  [Site "St. Petersburg  RUE"]
  [Date "1914.04.22"]
  [EventDate "1914.04.21"]
  [Round "2"]
  [Result "1/2-1/2"]
  [White "Alexander Alekhine"]
  [Black "Joseph Henry Blackburne"]
  [ECO "C61"]
  [WhiteElo "?"]
  [BlackElo "?"]
  [PlyCount "89"]
  
  1. e4 e5 2. Nf3 Nc6 3. Bb5 Nd4 4. Nxd4 exd4 5. O-O g6 6. d3
  Bg7 7. f4 c6 8. Bc4 d5 9. exd5 cxd5 10. Bb5+ Kf8 11. Nd2 Qa5
  12. a4 a6 13. Nb3 Qd8 14. Bd2 axb5 15. axb5 Rxa1 16. Bb4+ Ne7
  17. Qxa1 Bf6 18. Qa7 b6 19. Re1 Be6 20. Kh1 h5 21. Bxe7+ Qxe7
  22. Qxb6 Qb4 23. Qc5+ Qxc5 24. Nxc5 Bd8 25. Nxe6+ fxe6
  26. Rxe6 Kf7 27. Rd6 Be7 28. Rxd5 Rc8 29. c4 dxc3 30. bxc3
  Rxc3 31. Kg1 Ke6 32. Re5+ Kd6 33. Re3 Rb3 34. Kf1 Rb4 35. Re4
  Rb2 36. Re3 h4 37. Re4 Bf6 38. b6 Kd5 39. Re8 Rxb6 40. Kf2 Rb3
  41. Rg8 Rxd3 42. Rxg6 Ke6 43. g4 hxg3+ 44. hxg3 Kf5 45.Rg8
  1/2-1/2
  
  
  ---
  
  