Answers.Body: <p>Of course this has happened, but it depends on your definitions. With the definition that &quot;a blunder is a move that changes the game-theoretic state of the game&quot; (e.g. &quot;draw&quot; to &quot;loss&quot; or &quot;win&quot; to &quot;draw&quot;), then here's an <a href="https://chessbase.in/news/Grischuk-versus-Ding-Liren-World-Cup-2019" rel="nofollow noreferrer">example</a> where both Ding Liren and Alexander Grischuk were blissfully unaware of the blunder until after the end of the game.</p>
  <pre><code>[FEN &quot;&quot;]
  [White &quot;Grischuk, Alexander&quot;]
  [WhiteElo &quot;2759&quot;]
  [Black &quot;Ding, Liren&quot;]
  [BlackElo &quot;2811&quot;]
  [Result &quot;1/2-1/2&quot;]
  [startply &quot;26&quot;]
  
  1. d4 Nf6 
  2. c4 e6 
  3. Nf3 d5 
  4. g3 dxc4 
  5. Bg2 a6 
  6. O-O Nc6 
  7. e3 Rb8 
  8. Nfd2 e5 
  9. Bxc6+ bxc6 
  10. dxe5 Ng4 
  11. Nxc4 Be6 
  12. Qe2 h5 
  13. Rd1 Qc8 
  14. Qf3? Bd5 
  15. Rxd5 cxd5 
  16. Qxd5 Qf5! {Black threatens ...Qxf2+ and mate.} 
  17. f3! {Both Grischuk and Ding Liren saw this far and could not see a refutation of this move.} Qc2! {Black threatens ...Qxc1+, and ...Qf2+ followed by mate.} 
  18. Qc6+! {18.Nbd2? Qd1+ 19. Kg2 Qe2+ wins. White has to move the Queen so that the d2-knight is no longer pinned, and Nf1 becomes possible.} Kd8 
  19. Nbd2 Qd1+ 
  20. Nf1 {If White gets a single free move here, 21. Bd2 intending 22. Ba5 wins.} Nxh2! {20...Rh6? 21. Qe4 Nxh2? 22. Qh4+ and Qxh2 wins for White.} 
  21. Kxh2 {Just to illustrate how difficult the position is, see if you can calculate how Black wins after 21. Bd2.} Rh6!! {And Black wins because of the dual threats of ...Rxc6 and ...Qxf1. Comparatively 21...Qxf1? 22. e6 gives White enough counterplay to force a draw.}
  
  </code></pre>
  <p>Grischuk (White) went 14. Qf3? allowing Ding a game-winning continuation beginning with 14...Bd5, that was however not easy to spot by an unassisted human. After seven minutes Ding played (&quot;blundered&quot;) 14...Rb6 and the game was eventually drawn.</p>
  <p>However: given the complexity of the variation and how hard it is for a human to spot, can you fairly call 14. Qf3 or 14...Rb6 blunders?</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-07-28T06:03:24.310Z
Answers.Text: Can't figure out how to add the correct move numbers to the diagram, if anyone can please go ahead and edit the post.
Answers.UserDisplayName: Allure
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-07-28T08:33:28.093Z
Answers.Text: There is no way to start at a random number with the replayer as is, to my knowledge.  The only real solution is to put in the entire game and use [startply "x"] beneath the FEN.
Answers.UserDisplayName: Rewan Demontay
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-07-28T13:19:19.783Z
Answers.Text: @RewanDemontay, I added the whole game, but the [startply] param doesn't really do it for me? In the PGN the Param 'PlyCount' is mentioned for half moves, but that doesn't work either :-|
Answers.UserDisplayName: IT M
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-07-29T00:27:03.737Z
Answers.Text: @ITM It counts by half moves, aka a ply. You put in the move number instead.
Answers.UserDisplayName: Rewan Demontay
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-07-28T05:59:32.790Z
Answers.LastActivityDate: 2024-01-31T02:39:07.397Z
Answers.LastEditDate: 2024-01-31T02:39:07.397Z
Answers.UserDisplayName: Allure
Body: <p>Any high-level GM games where somebody makes a big blunder but was in blissful ignorance about how bad the move was until several moves after the blunder?</p>
  <p>EDIT thanks to comment: classical time format, not blitz (where blunders are common)</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2023-07-27T15:11:26.473Z
Comments.Text: You could probably find hundreds of lichess Blitz games, or blunders happening in mutual time trouble.
  
  Are you asking for classical time controls tournament games?
Comments.UserDisplayName: Hauptideal
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2023-07-27T22:30:49.137Z
Comments.Text: @Hauptideal yes pretty much
Comments.UserDisplayName: Chris Sanders
Tags: <grandmaster><master-games><blunder>
Title: Blunders that they didn't realise for some time
ThreadText: # Blunders that they didn't realise for some time
  
  (Asked by: username_0 on 2023-07-27)
  
  Any high-level GM games where somebody makes a big blunder but was in blissful ignorance about how bad the move was until several moves after the blunder?
  
  EDIT thanks to comment: classical time format, not blitz (where blunders are common)
  
  **Tags:** grandmaster, master-games, blunder
  
  > **Comments:**
  > **username_1**: You could probably find hundreds of lichess Blitz games, or blunders happening in mutual time trouble.  Are you asking for classical time controls tournament games?  
  > **username_0**: @username_1 yes pretty much  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_2 on 2023-07-28. Score: 2 | Accepted answer
  
  Of course this has happened, but it depends on your definitions. With the definition that "a blunder is a move that changes the game-theoretic state of the game" (e.g. "draw" to "loss" or "win" to "draw"), then here's an [example](https://chessbase.in/news/Grischuk-versus-Ding-Liren-World-Cup-2019) where both Ding Liren and Alexander Grischuk were blissfully unaware of the blunder until after the end of the game.
  
  ```
  [FEN ""]
  [White "Grischuk, Alexander"]
  [WhiteElo "2759"]
  [Black "Ding, Liren"]
  [BlackElo "2811"]
  [Result "1/2-1/2"]
  [startply "26"]
  
  1. d4 Nf6 
  2. c4 e6 
  3. Nf3 d5 
  4. g3 dxc4 
  5. Bg2 a6 
  6. O-O Nc6 
  7. e3 Rb8 
  8. Nfd2 e5 
  9. Bxc6+ bxc6 
  10. dxe5 Ng4 
  11. Nxc4 Be6 
  12. Qe2 h5 
  13. Rd1 Qc8 
  14. Qf3? Bd5 
  15. Rxd5 cxd5 
  16. Qxd5 Qf5! {Black threatens ...Qxf2+ and mate.} 
  17. f3! {Both Grischuk and Ding Liren saw this far and could not see a refutation of this move.} Qc2! {Black threatens ...Qxc1+, and ...Qf2+ followed by mate.} 
  18. Qc6+! {18.Nbd2? Qd1+ 19. Kg2 Qe2+ wins. White has to move the Queen so that the d2-knight is no longer pinned, and Nf1 becomes possible.} Kd8 
  19. Nbd2 Qd1+ 
  20. Nf1 {If White gets a single free move here, 21. Bd2 intending 22. Ba5 wins.} Nxh2! {20...Rh6? 21. Qe4 Nxh2? 22. Qh4+ and Qxh2 wins for White.} 
  21. Kxh2 {Just to illustrate how difficult the position is, see if you can calculate how Black wins after 21. Bd2.} Rh6!! {And Black wins because of the dual threats of ...Rxc6 and ...Qxf1. Comparatively 21...Qxf1? 22. e6 gives White enough counterplay to force a draw.}
  
  ```
  
  Grischuk (White) went 14. Qf3? allowing Ding a game-winning continuation beginning with 14...Bd5, that was however not easy to spot by an unassisted human. After seven minutes Ding played ("blundered") 14...Rb6 and the game was eventually drawn.
  
  However: given the complexity of the variation and how hard it is for a human to spot, can you fairly call 14. Qf3 or 14...Rb6 blunders?
  
  > **Comments:**
  > **username_2**: Can't figure out how to add the correct move numbers to the diagram, if anyone can please go ahead and edit the post.  
  > **username_3**: There is no way to start at a random number with the replayer as is, to my knowledge.  The only real solution is to put in the entire game and use [startply "x"] beneath the FEN.  
  > **username_4**: @username_3, I added the whole game, but the [startply] param doesn't really do it for me? In the PGN the Param 'PlyCount' is mentioned for half moves, but that doesn't work either :-|  
  > **username_3**: @ITM It counts by half moves, aka a ply. You put in the move number instead.  
  
  ---
  
  