Answers.Body: <p>In 2009, GM Nurlan Ibrayev of Kazakhstan (rated 2407 at the time) <a href="http://www.chessbase.com/newsdetail.asp?newsid=5144" rel="noreferrer">lost a classical time control game</a> to 9-year-old Hetul Shah of India, who then had a FIDE rating of 1817. Shah's current rating, now three years after that game, is 1979, not so much higher than it was at the time of his upset victory. So this game wasn't a case of Ibrayev running up against some seriously underrated prodigy whose rating was about to shoot up several hundred points. To the contrary, this seems to be exactly the sort of game you are after: a much weaker player having a good day and taking a grandmaster scalp, with the black pieces no less!</p>
  
  <pre><code>[FEN ""]
  [Event "7th Parsvnath International Open"]
  [Site "Delhi"]
  [Date "2009.01.11"]
  [EventDate "2009.01.11"]
  [Round "1.36"]
  [Result "0-1"]
  [White "Nurlan Ibrayev"]
  [Black "Hetul Shah"]
  [WhiteElo "2407"]
  [BlackElo "1817"]
  [PlyCount "88"]
  
  1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.O-O Be7 6.Re1 b5 7.Bb3 d6 8.c3 O-O
  9.h3 Na5 10.Bc2 c5 11.d4 Qc7 12.Nbd2 cxd4 13.cxd4 Bd7 14.Nf1 Rfc8 15.Ne3 Nc6
  16.a3 Bf8 17.b3 Nxd4 18.Nxd4 Qc3 19.Ne2 Qxa1 20.Qd2 d5 21.b4 d4 22.Nd1 Rxc2
  23.Qxc2 Rc8 24.Qd2 Nxe4 25.Qd3 Nd6 26.Bb2 Qa2 27.f4 Qc4 28.Qb1 d3 29.Ne3 Qe4
  30.Nc3 Qxf4 31.Ncd5 Qg3 32.Nf1 Qg6 33.Bxe5 Nc4 34.Nf4 Qb6+ 35.Kh1 Nxe5 36.Rxe5
  Bd6 37.Re4 Bc6 38.Qc1 Qb7 39.Re1 Bxg2+ 40.Nxg2 Rxc1 41.Rxc1 Bf4 42.Rc3 d2
  43.Rd3 h6 44.Kg1 Qb6+ 0-1
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2012-06-25T20:30:04.170Z
Answers.LastActivityDate: 2012-11-14T19:22:07.967Z
Answers.LastEditDate: 2012-11-14T19:22:07.967Z
Answers.UserDisplayName: ETD
Answers.Body: <p>Late to the party, but while Anand losing to a guy, who was rated 400 points below him was, clearly, a huge upset; an IM, who was over 2400 at one point, and 2368 when that game was played is definitely strong enough to take advantage if Anand makes an error. </p>
  
  <p>This still probably beats all upsets I have ever heard of. In the first round, GM John Fedorowicz, rated 2479 at the time (I cannot find this to prove it, but I am recall his USCF rating being in the mid-2500's as well), lost to a 1714 player at the 1980 U.S. Open!</p>
  
  <p>I still remember this because I was a really new player, and saw this game in "Chess Life and Review" (Later shortened to "Chess Life"), and I was amazed. Nevertheless, Fed brushed off the early setback, and tied for first.</p>
  
  <p><a href="http://www.chessgames.com/perl/chessgame?gid=1609849" rel="noreferrer">http://www.chessgames.com/perl/chessgame?gid=1609849</a></p>
  
  <pre><code>[Title "W Stanley Davis-John Fedorowicz, 81st US Open, 8/3/1980"]
  [FEN ""]
  
  1.Nf3 e6 2.e3 b6 3.b3 Bb7 4.Bb2 c5 5.Be2 Nf6 6.d3 d5 7.Nbd2 Be7 8.Ne5 O-O 9.O-O Re8 10.f4 Bf8 11.Qe1 a5 12.g4 a4 13.Rc1 axb3 14.axb3 Ra2 15.Ba1 Na6 16.g5 Nd7 17.Bh5 Nxe5 18.Bxe5 Nb4 19.Qh4 Nxc2 20.Rf3 Nxe3 21.Rxe3 Rxd2 22.Rh3 c4 23.Bf6 Bc5+ 24.Kf1 Bf2 25.Bxf7+ Kf8 26.Qxh7 gxf6 27.Bg6 1-0
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-09-08T12:21:29.760Z
Answers.LastActivityDate: 2019-09-08T12:21:29.760Z
Answers.UserDisplayName: PhishMaster
Answers.Body: <p>The 2017 Isle of Man Masters tournament provided a couple of these shock results.</p>
  
  <p>First the fairy tale story of an aging, declining US GM overturning an almost 400 point rating difference to beat one of the pre-tournament favourites, ex world champion Vladimir Kramnik.</p>
  
  <pre><code>[fen ""]
  [Event "Isle of Man Masters"]
  [Site "Douglas IMN"]
  [Date "2017.09.25"]
  [EventDate "2017.09.23"]
  [Round "3.28"]
  [Result "1-0"]
  [White "James Tarjan (2412)"]
  [Black "Vladimir Kramnik (2803)"]
  [ECO "A12"]
  [WhiteElo "2412"]
  [BlackElo "2803"]
  [PlyCount "111"]
  
  1. c4 Nf6 2. g3 c6 3. Nf3 d5 4. b3 Bg4 5. Bg2 e6 6. O-O Nbd7 7. Bb2 Bd6 8. d3 O-O 9. Nbd2 Re8 10. h3 Bh5 11. Re1 a5 12. a3 e5 13. cxd5 cxd5 14. Nh4 Nc5 15. Qc2 Ne6 16. Rac1 Nd4 17. Qd1 Nb5 18. Nb1 Qd7 19. Kh2 Ra6 20. Nf3 e4 21. dxe4 Nxe4 22. Rf1 Bb8 23. Nc3 Nbxc3 24. Bxc3 Rae6 25. Be1 h6 26. Rc2 Ba7 27. Qc1 Bb6 28. e3 Qb5 29. Nd4 Bxd4 30. exd4 Bf3 31. Bxf3 Nxg3 32. fxg3 Qxf1 33. Bf2 Qd3 34. Rc3 Qf5 35. Kg2 Rf6 36. Qc2 Qd7 37. g4 Rc6 38. Rc5 Rd8 39. Qf5 Rxc5 40. Qxd7 Rxd7 41. dxc5 d4 42. Kf1 d3 43. Ke1 d2+ 44. Kd1 Kf8 45. Bg3 Ke7 46. Bd6+ Ke6 47. Kxd2 b6 48. Ke3 bxc5 49. Bxc5 Rd8 50. b4 axb4 51. axb4 f5 52. b5 fxg4 53. hxg4 g6 54. b6 h5 55. g5 Kd7 56. b7 1-0
  </code></pre>
  
  <p>In the first round an obscure 70 year old English player took a draw by repetition in a winning position against a GM rated almost 700 points higher.</p>
  
  <pre><code>[fen ""]
  [Event "Isle of Man Masters"]
  [Site "Douglas IMN"]
  [Date "2017.09.23"]
  [EventDate "2017.09.23"]
  [Round "1.14"]
  [Result "1/2-1/2"]
  [White "Zaki Harari (2027)"]
  [Black "Maxim Rodshtein (2695)"]
  [ECO "B21"]
  [WhiteElo "2027"]
  [BlackElo "2695"]
  [PlyCount "147"]
  
  1. e4 c5 2. d4 cxd4 3. c3 d3 4. Bxd3 Nc6 5. c4 g6 6. Nf3 Bg7 7. O-O d6 8. h3 Nf6 9. Nc3 O-O 10. Be3 Nd7 11. Rc1 Nde5 12. Be2 b6 13. Qd2 Bb7 14. Rfd1 Rc8 15. b3 Nxf3+ 16. Bxf3 Ne5 17. Be2 Nd7 18. Bh6 Nf6 19. Bxg7 Kxg7 20. Bf3 Qc7 21. h4 Qb8 22. h5 Rc5 23. h6+ Kg8 24. Nd5 Bxd5 25. exd5 Rfc8 26. Re1 R8c7 27. a4 Qf8 28. Qf4 a5 29. Qe3 Kh8 30. g4 Ng8 31. g5 f6 32. gxf6 exf6 33. Qf4 Re7 34. Kf1 Re5 35. Rxe5 dxe5 36. Qd2 Qd6 37. Rd1 Rc7 38. Bg2 g5 39. Bh3 Nxh6 40. Be6 Ng8 41. Qe2 Ne7 42. Qf3 Kg7 43. Qh5 Ng6 44. Bf5 Re7 45. Rd3 Nf8 46. Rh3 Kg8 47. Be4 Rg7 48. Bf5 Re7 49. Be4 Qd7 50. Rf3 Rf7 51. Bf5 Qe7 52. Rd3 Qd6 53. Rh3 Rg7 54. Rf3 Qd8 55. Rh3 Ra7 56. Rd3 Qd6 57. Rh3 Rf7 58. Be4 Qa3 59. Bf5 Re7 60. Qd1 Qd6 61. Qd3 Rg7 62. Rh6 g4 63. Qg3 Rg5 64. Be4 Kg7 65. Qh4 Qe7 66. d6 Qf7 67. d7 Qe7 68. Rxh7+ Nxh7 69. Qxh7+ Kf8 70. Qh8+ Rg8 71. Qh6+ Rg7 72. Qh8+ Rg8 73. Qh6+ Rg7 74. Qh8+ 1/2-1/2
  </code></pre>
  
  <p>Bd5 crying out to be played instead of Qh8.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-07-24T15:43:55.830Z
Answers.LastActivityDate: 2019-07-24T15:43:55.830Z
Answers.UserDisplayName: Brian Towers
Answers.Body: <p>Here are two examples drawn from Fox and James, <em>The Complete Chess Addict</em>, pub. 1987.</p>
  <pre><code>[Title &quot;Gilberto Garcia - Borislav Ivkov, Capablanca MT 1965&quot;]
  [fen &quot;&quot;]
  
  1.d4 Nf6 2.c4 e6 3.Nf3 d5 4.e3 c5
  5.dxc5 Bxc5 6.b3 O-O 7.Qc2 Nc6 8.a3 Bb6
  9.Bb2 Re8 10.Nc3 d4 11.Rd1 e5 12.e4 Ng4
  13.Na4 Ba5+ 14.b4 Nxb4 15.axb4 Bxb4+ 16.Rd2 Bd7
  17.Bc1 b5 18.Nb2 Rc8
  19.Be2 Be6 20.O-O bxc4 21.Nxc4 Qc7 22.Qa4 Bxd2 23.Bxd2 Bxc4
  24.Rc1 Qc6 25.Rxc4 Qxe4 26.Rxc8 Rxc8 27.Qd7 Rf8 28.Bf1 Nf6
  29.Qc7 Nd5 30.Qd7 Nf4 31.h3 Qb1
  32.Be1? {Best are g3/Bxf4.} e4
  33.Qf5 Ne6 34.Bd2 g6
  35.Qf6 exf3 36.g4 d3 37.Bc3 {thr Qh8#} 1-0
  </code></pre>
  <p>The above game was played in round 20 of 21. After 19 rounds, Ivkov was leading, and was expected to beat the weaker Garcia and clinch first place. He lost his last two games and finished equal 4th.</p>
  <pre><code>[Title &quot;Jose Raul Capablanca - Alexander Kevitz, simul, 1924&quot;]
  [fen &quot;&quot;]
  
  1.b4 d5 2.Bb2 Bf5 3.e3 e6 4.f4 Nf6
  5.Nf3 Bxb4 6.Nc3 Nbd7 7.Ne2 Ng4 8.c3 Be7
  9.h3 Nc5 {thr Nb3#}
  10.Ng3 Bh4 11.Nxh4 Qxh4 12.Qf3 Nxe3
  13.Qf2 Nxf1 {White resigned} 0-1
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-01-26T00:38:18.960Z
Answers.Text: I don't think it counts as an upset when the weaker player wins a game in a simul.
Answers.UserDisplayName: bof
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-01-25T08:54:46.940Z
Answers.LastActivityDate: 2022-01-25T08:54:46.940Z
Answers.UserDisplayName: Rosie F
Answers.Body: <p>In a 1929 against Fritz Saemisch, a lesser master, former World Champion J. R. Capablanca blundered away a piece on the 9th move, and resigned some 50-odd moves later.</p>
  
  <p><a href="http://www.chessgames.com/perl/chessgame?gid=1066901" rel="nofollow">http://www.chessgames.com/perl/chessgame?gid=1066901</a></p>
  
  <p>It was reported that Capablanca'ss wife or mistress (or possibly both) had just entered the room. In any event, the grandmaster LOST the game.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2012-10-08T21:12:01.183Z
Answers.Text: Giving this as an answer to this particular question doesn't seem quite fair to Saemisch. He was no Capablanca of course, but he was one of the top players in the world for many years. Chessmetrics, for instance, puts him at #14 in 1929 (while Capablanca was #2): http://www.chessmetrics.com/cm/DL/DL80.htm. That's an upset, sure, but one between world-class players, while this question asks for examples where "a much weaker player succeeded against an IM or GM."
Answers.UserDisplayName: ETD
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2012-11-18T07:28:56.833Z
Answers.Text: Also I'm not sure he's much after piece blunders, especially if that's meant for study.
Answers.UserDisplayName: Nikana Reklawyks
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2012-10-08T20:33:07.037Z
Answers.LastActivityDate: 2012-10-08T20:33:07.037Z
Answers.UserDisplayName: Tom Au
Answers.Body: <p>This game comes to mind:</p>
  
  <p>It was a first game in a 2 game match of the first round knock out FIDE championship. Anand rated at 2770 was I believe the highest rated player in the event. Touzane, I believe, was not a professional player. Touzane won the first game. Despite the first game win for Touzane, Anand won the second, and then the tie-break. Nevertheless, Anand losing to a player rated 400+ below him was quite a shocker.</p>
  
  <pre><code>[FEN ""]
  [Event "FIDE WCh KO"]
  [Site "Moscow RUS"]
  [Date "2001.01.02"]
  [EventDate "2001.11.27"]
  [Round "1.1"]
  [Result "0-1"]
  [White "Viswanathan Anand"]
  [Black "Olivier Touzane"]
  [ECO "C42"]
  [WhiteElo "2770"]
  [BlackElo "2368"]
  [PlyCount "78"]
  
  1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Nc6
  7. O-O Be7 8. c4 Nf6 9. Nc3 O-O 10. Re1 Be6 11. cxd5 Nxd5
  12. a3 Bf6 13. Be4 h6 14. Bc2 Nxc3 15. bxc3 Bc4 16. Nd2 Bd5
  17. Rb1 Bg5 18. c4 Bxd2 19. cxd5 Bxe1 20. dxc6 Ba5 21. Qd3 g6
  22. cxb7 Rb8 23. Bxh6 Re8 24. Qf3 Re6 25. Bb3 Rf6 26. Qg4 Rb6
  27. Bg5 Qe8 28. Qf3 R8xb7 29. h4 Qd7 30. g4 Rxb3 31. Rxb3 Rxb3
  32. Qxb3 Qxg4+ 33. Kf1 Qxd4 34. Be3 Qa1+ 35. Kg2 Bb6 36. Bxb6
  axb6 37. Qg3 Qc1 38. h5 Qc6+ 39. Kf1 Qh1+ 0-1
  </code></pre>
  
  <p><a href="http://www.chessgames.com/perl/chessgame?gid=1209549" rel="nofollow noreferrer">Anand - Touzane</a></p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2012-06-15T07:58:53.993Z
Answers.Text: I really like it :-)
Answers.UserDisplayName: Landei
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2012-06-16T16:18:02.250Z
Answers.Text: I thought this was interesting, so I ran it through Phalanx-Scid.  Anand has a slight pull and a nice attack through move 25.  The exchange sacrifice got my attention!  After `25. Be3 `, however, Anand's  advantage drops from 1.5 to 1.3 pts, which is probably still enough for a win against Touzane.  Now things begin to come apart for Anand.  `26. Qg4?` misses that the rook on f6 is defending the g7 pawn against the Q, not the B on b3.  When the queen moves, _and leaves the rook on b1 and the pawn on b7 undefended_, things get interesting.  (more to come)
Answers.UserDisplayName: Tony Ennis
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2012-06-16T16:50:29.637Z
Answers.Text: Now Anand's advantage is down to .3 points.  Phalanx says, `26. ... Rb6 27. Ba2 R8xb7 28. Rc1 Qf6 29. Qc8+ Kh7 30.Qh3 Kg8 31. Qc8+`, apparently considering a draw by repetition.  Black of course can't allow the discovered check.  Phalanx doesn't like `27. Bg5` stating it loses another half-pawn to `27. ... Qe8 28. h3 R8xb7 29. Qh4 c5 30. Rc1 Qd7 31. Rxc5 Rxb3 32. Rxa5 Rb1+ 33. Kh2`  So what's come about has been related to black's excellent 26th move, which pinned the bishop on b3 and exploited Anand's weak back rank. (more to come)
Answers.UserDisplayName: Tony Ennis
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2012-06-16T17:38:15.567Z
Answers.Text: Ok, I got curious and found out that Phalanx is a cool program but not in the top rated engines. I switched to Stockfish.  After `27. Bg5` black is winning, if ever so slightly - about a quarter of a pawn.  Then comes `27. ... Qe8 28. Qf3 [h3 - Stockfish]` which costs a full point while still not addressing the back-rank weakness.  Touzane finds the right move, and Anand plays `29. h4 [g4 - Stockfish]` which doesn't help (or hurt) his game. (more to come)
Answers.UserDisplayName: Tony Ennis
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2012-06-16T17:50:13.900Z
Answers.Text: What's interesting is that for the last few moves, Touzane is finding all the right moves according to Stockfish. Anand is not.  Now, bear in mind Anand and Touzane are both more highly rated than this program on this computer...  So this analysis is more of an assist than some gospel truth. After `30. g4` (keeping the back Q off of f6) Touzane exploits white's overloaded queen: `30. ... Rxb3 31. Rxb3 Rxb3 32. Qxb3 Qxg4+`.  Now white's d-pawn is forfeit, white pawns are all islands, and black has a passed pawn.
Answers.UserDisplayName: Tony Ennis
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2012-06-16T18:48:53.123Z
Answers.Text: For all that, The computer rates Anand 1.25 pawns behind.  Perhaps Anand can pull out the draw.  Starting now, for brevity, I'm putting Stockfish's moves in brackets.  But `33. Kf1 [Qg3]` causes more erosion in Anand's position.  Black finds the moves again while Anand does not with `33. ... Qxd4 34. Be3 [Qf3] Qa1+ 35. Kg2 [Ke2] Bb6 36. Bxb6 [Kg3]` and white's position continues to erode. He's now down by over 2 points. Now `36. ... axb6 37. Qg3 Qc1 [c5]` and now it's Touzane who gives some back.  Anand's position looks lost just the same.
Answers.UserDisplayName: Tony Ennis
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2012-06-16T19:06:17.940Z
Answers.Text: At this point, if Touzane can get the queens off the board, Anand will resign immediately.  It becomes moot, since Anand's `39. Kf1` is an instant loser.  Stockfish recommended `39. Kh2` though I don't understand since black's Qd6 will take the queens off. White is down by 3.23 points.  `39. ... Qh1+ 0-1` and Bob's your uncle.
Answers.UserDisplayName: Tony Ennis
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2012-06-16T19:25:26.463Z
Answers.Text: Looking at a variation, `39. Kh2 Qd6` leads to a -2.4 score, so it's also very terminal.  White keeps the queens on the board with `40. f4`, which is followed by `40. ... Qd2+ 41. Kh3 Qd1 42. hxg6 Qh5+ 43. Kg2 Qxg6`
Answers.UserDisplayName: Tony Ennis
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2012-06-14T13:12:12.617Z
Answers.LastActivityDate: 2019-09-08T04:33:20.660Z
Answers.LastEditDate: 2019-09-08T04:33:20.660Z
Answers.UserDisplayName: Akavall
Body: <p>I'd like to study examples where a much weaker player succeeded against an IM or GM.</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2012-06-14T08:22:58.030Z
Comments.Text: Related: http://chess.stackexchange.com/questions/728/has-a-highly-rated-gm-ever-lost-to-a-low-rated-opponent-who-didnt-go-on-to-beco
Comments.UserDisplayName: ETD
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2012-06-14T08:28:17.463Z
Comments.Text: Yes, I overlooked this question. Still, only one answer (a game which was probably made up), so I hope for more...
Comments.UserDisplayName: Landei
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2019-07-26T02:10:35.973Z
Comments.Text: [Browne–Taha, Skopje, 1972](http://www.chessgames.com/perl/chessgame?gid=1282359) was a pretty famous upset, but I don't know what Taha's rating was.
Comments.UserDisplayName: bof
Tags: <rating>
Title: What are some examples of wins by a much weaker player?
ThreadText: # What are some examples of wins by a much weaker player?
  
  (Asked by: username_0 on 2012-06-14)
  
  I'd like to study examples where a much weaker player succeeded against an IM or GM.
  
  **Tags:** rating
  
  > **Comments:**
  > **username_1**: Related: http://chess.stackexchange.com/questions/728/has-a-highly-rated-gm-ever-lost-to-a-low-rated-opponent-who-didnt-go-on-to-beco  
  > **username_0**: Yes, I overlooked this question. Still, only one answer (a game which was probably made up), so I hope for more...  
  > **username_2**: [Browne–Taha, Skopje, 1972](http://www.chessgames.com/perl/chessgame?gid=1282359) was a pretty famous upset, but I don't know what Taha's rating was.  
  
  ---
  
  ## 6 answers
  
  ### Answer by username_8 on 2012-06-14. Score: 12 | Accepted answer
  
  This game comes to mind:
  It was a first game in a 2 game match of the first round knock out FIDE championship. Anand rated at 2770 was I believe the highest rated player in the event. Touzane, I believe, was not a professional player. Touzane won the first game. Despite the first game win for Touzane, Anand won the second, and then the tie-break. Nevertheless, Anand losing to a player rated 400+ below him was quite a shocker.
  [FEN ""]
  [Event "FIDE WCh KO"]
  [Site "Moscow RUS"]
  [Date "2001.01.02"]
  [EventDate "2001.11.27"]
  [Round "1.1"]
  [Result "0-1"]
  [White "Viswanathan Anand"]
  [Black "Olivier Touzane"]
  [ECO "C42"]
  [WhiteElo "2770"]
  [BlackElo "2368"]
  [PlyCount "78"]
  
  1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Nc6
  7. O-O Be7 8. c4 Nf6 9. Nc3 O-O 10. Re1 Be6 11. cxd5 Nxd5
  12. a3 Bf6 13. Be4 h6 14. Bc2 Nxc3 15. bxc3 Bc4 16. Nd2 Bd5
  17. Rb1 Bg5 18. c4 Bxd2 19. cxd5 Bxe1 20. dxc6 Ba5 21. Qd3 g6
  22. cxb7 Rb8 23. Bxh6 Re8 24. Qf3 Re6 25. Bb3 Rf6 26. Qg4 Rb6
  27. Bg5 Qe8 28. Qf3 R8xb7 29. h4 Qd7 30. g4 Rxb3 31. Rxb3 Rxb3
  32. Qxb3 Qxg4+ 33. Kf1 Qxd4 34. Be3 Qa1+ 35. Kg2 Bb6 36. Bxb6
  axb6 37. Qg3 Qc1 38. h5 Qc6+ 39. Kf1 Qh1+ 0-1
  
  Anand - Touzane
  
  > **Comments:**
  > **username_0**: I really like it :-)  
  > **username_9**: I thought this was interesting, so I ran it through Phalanx-Scid.  Anand has a slight pull and a nice attack through move 25.  The exchange sacrifice got my attention!  After `25. Be3 `, however, Anand's  advantage drops from 1.5 to 1.3 pts, which is probably still enough for a win against Touzane.  Now things begin to come apart for Anand.  `26. Qg4?` misses that the rook on f6 is defending the g7 pawn against the Q, not the B on b3.  When the queen moves, _and leaves the rook on b1 and the pawn on b7 undefended_, things get interesting.  (more to come)  
  > **username_9**: Now Anand's advantage is down to .3 points.  Phalanx says, `26. ... Rb6 27. Ba2 R8xb7 28. Rc1 Qf6 29. Qc8+ Kh7 30.Qh3 Kg8 31. Qc8+`, apparently considering a draw by repetition.  Black of course can't allow the discovered check.  Phalanx doesn't like `27. Bg5` stating it loses another half-pawn to `27. ... Qe8 28. h3 R8xb7 29. Qh4 c5 30. Rc1 Qd7 31. Rxc5 Rxb3 32. Rxa5 Rb1+ 33. Kh2`  So what's come about has been related to black's excellent 26th move, which pinned the bishop on b3 and exploited Anand's weak back rank. (more to come)  
  > **username_9**: Ok, I got curious and found out that Phalanx is a cool program but not in the top rated engines. I switched to Stockfish.  After `27. Bg5` black is winning, if ever so slightly - about a quarter of a pawn.  Then comes `27. ... Qe8 28. Qf3 [h3 - Stockfish]` which costs a full point while still not addressing the back-rank weakness.  Touzane finds the right move, and Anand plays `29. h4 [g4 - Stockfish]` which doesn't help (or hurt) his game. (more to come)  
  > **username_9**: What's interesting is that for the last few moves, Touzane is finding all the right moves according to Stockfish. Anand is not.  Now, bear in mind Anand and Touzane are both more highly rated than this program on this computer...  So this analysis is more of an assist than some gospel truth. After `30. g4` (keeping the back Q off of f6) Touzane exploits white's overloaded queen: `30. ... Rxb3 31. Rxb3 Rxb3 32. Qxb3 Qxg4+`.  Now white's d-pawn is forfeit, white pawns are all islands, and black has a passed pawn.  
  > **username_9**: For all that, The computer rates Anand 1.25 pawns behind.  Perhaps Anand can pull out the draw.  Starting now, for brevity, I'm putting Stockfish's moves in brackets.  But `33. Kf1 [Qg3]` causes more erosion in Anand's position.  Black finds the moves again while Anand does not with `33. ... Qxd4 34. Be3 [Qf3] Qa1+ 35. Kg2 [Ke2] Bb6 36. Bxb6 [Kg3]` and white's position continues to erode. He's now down by over 2 points. Now `36. ... axb6 37. Qg3 Qc1 [c5]` and now it's Touzane who gives some back.  Anand's position looks lost just the same.  
  > **username_9**: At this point, if Touzane can get the queens off the board, Anand will resign immediately.  It becomes moot, since Anand's `39. Kf1` is an instant loser.  Stockfish recommended `39. Kh2` though I don't understand since black's Qd6 will take the queens off. White is down by 3.23 points.  `39. ... Qh1+ 0-1` and Bob's your uncle.  
  > **username_9**: Looking at a variation, `39. Kh2 Qd6` leads to a -2.4 score, so it's also very terminal.  White keeps the queens on the board with `40. f4`, which is followed by `40. ... Qd2+ 41. Kh3 Qd1 42. hxg6 Qh5+ 43. Kg2 Qxg6`  
  
  ---
  
  ### Answer by username_1 on 2012-06-25. Score: 15
  
  In 2009, GM Nurlan Ibrayev of Kazakhstan (rated 2407 at the time) lost a classical time control game to 9-year-old Hetul Shah of India, who then had a FIDE rating of 1817. Shah's current rating, now three years after that game, is 1979, not so much higher than it was at the time of his upset victory. So this game wasn't a case of Ibrayev running up against some seriously underrated prodigy whose rating was about to shoot up several hundred points. To the contrary, this seems to be exactly the sort of game you are after: a much weaker player having a good day and taking a grandmaster scalp, with the black pieces no less!
  [FEN ""]
  [Event "7th Parsvnath International Open"]
  [Site "Delhi"]
  [Date "2009.01.11"]
  [EventDate "2009.01.11"]
  [Round "1.36"]
  [Result "0-1"]
  [White "Nurlan Ibrayev"]
  [Black "Hetul Shah"]
  [WhiteElo "2407"]
  [BlackElo "1817"]
  [PlyCount "88"]
  
  1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.O-O Be7 6.Re1 b5 7.Bb3 d6 8.c3 O-O
  9.h3 Na5 10.Bc2 c5 11.d4 Qc7 12.Nbd2 cxd4 13.cxd4 Bd7 14.Nf1 Rfc8 15.Ne3 Nc6
  16.a3 Bf8 17.b3 Nxd4 18.Nxd4 Qc3 19.Ne2 Qxa1 20.Qd2 d5 21.b4 d4 22.Nd1 Rxc2
  23.Qxc2 Rc8 24.Qd2 Nxe4 25.Qd3 Nd6 26.Bb2 Qa2 27.f4 Qc4 28.Qb1 d3 29.Ne3 Qe4
  30.Nc3 Qxf4 31.Ncd5 Qg3 32.Nf1 Qg6 33.Bxe5 Nc4 34.Nf4 Qb6+ 35.Kh1 Nxe5 36.Rxe5
  Bd6 37.Re4 Bc6 38.Qc1 Qb7 39.Re1 Bxg2+ 40.Nxg2 Rxc1 41.Rxc1 Bf4 42.Rc3 d2
  43.Rd3 h6 44.Kg1 Qb6+ 0-1
  
  
  ---
  
  ### Answer by username_3 on 2019-09-08. Score: 5
  
  Late to the party, but while Anand losing to a guy, who was rated 400 points below him was, clearly, a huge upset; an IM, who was over 2400 at one point, and 2368 when that game was played is definitely strong enough to take advantage if Anand makes an error. 
  This still probably beats all upsets I have ever heard of. In the first round, GM John Fedorowicz, rated 2479 at the time (I cannot find this to prove it, but I am recall his USCF rating being in the mid-2500's as well), lost to a 1714 player at the 1980 U.S. Open!
  I still remember this because I was a really new player, and saw this game in "Chess Life and Review" (Later shortened to "Chess Life"), and I was amazed. Nevertheless, Fed brushed off the early setback, and tied for first.
  http://www.chessgames.com/perl/chessgame?gid=1609849
  [Title "W Stanley Davis-John Fedorowicz, 81st US Open, 8/3/1980"]
  [FEN ""]
  
  1.Nf3 e6 2.e3 b6 3.b3 Bb7 4.Bb2 c5 5.Be2 Nf6 6.d3 d5 7.Nbd2 Be7 8.Ne5 O-O 9.O-O Re8 10.f4 Bf8 11.Qe1 a5 12.g4 a4 13.Rc1 axb3 14.axb3 Ra2 15.Ba1 Na6 16.g5 Nd7 17.Bh5 Nxe5 18.Bxe5 Nb4 19.Qh4 Nxc2 20.Rf3 Nxe3 21.Rxe3 Rxd2 22.Rh3 c4 23.Bf6 Bc5+ 24.Kf1 Bf2 25.Bxf7+ Kf8 26.Qxh7 gxf6 27.Bg6 1-0
  
  
  ---
  
  ### Answer by username_4 on 2019-07-24. Score: 5
  
  The 2017 Isle of Man Masters tournament provided a couple of these shock results.
  First the fairy tale story of an aging, declining US GM overturning an almost 400 point rating difference to beat one of the pre-tournament favourites, ex world champion Vladimir Kramnik.
  [fen ""]
  [Event "Isle of Man Masters"]
  [Site "Douglas IMN"]
  [Date "2017.09.25"]
  [EventDate "2017.09.23"]
  [Round "3.28"]
  [Result "1-0"]
  [White "James Tarjan (2412)"]
  [Black "Vladimir Kramnik (2803)"]
  [ECO "A12"]
  [WhiteElo "2412"]
  [BlackElo "2803"]
  [PlyCount "111"]
  
  1. c4 Nf6 2. g3 c6 3. Nf3 d5 4. b3 Bg4 5. Bg2 e6 6. O-O Nbd7 7. Bb2 Bd6 8. d3 O-O 9. Nbd2 Re8 10. h3 Bh5 11. Re1 a5 12. a3 e5 13. cxd5 cxd5 14. Nh4 Nc5 15. Qc2 Ne6 16. Rac1 Nd4 17. Qd1 Nb5 18. Nb1 Qd7 19. Kh2 Ra6 20. Nf3 e4 21. dxe4 Nxe4 22. Rf1 Bb8 23. Nc3 Nbxc3 24. Bxc3 Rae6 25. Be1 h6 26. Rc2 Ba7 27. Qc1 Bb6 28. e3 Qb5 29. Nd4 Bxd4 30. exd4 Bf3 31. Bxf3 Nxg3 32. fxg3 Qxf1 33. Bf2 Qd3 34. Rc3 Qf5 35. Kg2 Rf6 36. Qc2 Qd7 37. g4 Rc6 38. Rc5 Rd8 39. Qf5 Rxc5 40. Qxd7 Rxd7 41. dxc5 d4 42. Kf1 d3 43. Ke1 d2+ 44. Kd1 Kf8 45. Bg3 Ke7 46. Bd6+ Ke6 47. Kxd2 b6 48. Ke3 bxc5 49. Bxc5 Rd8 50. b4 axb4 51. axb4 f5 52. b5 fxg4 53. hxg4 g6 54. b6 h5 55. g5 Kd7 56. b7 1-0
  
  In the first round an obscure 70 year old English player took a draw by repetition in a winning position against a GM rated almost 700 points higher.
  [fen ""]
  [Event "Isle of Man Masters"]
  [Site "Douglas IMN"]
  [Date "2017.09.23"]
  [EventDate "2017.09.23"]
  [Round "1.14"]
  [Result "1/2-1/2"]
  [White "Zaki Harari (2027)"]
  [Black "Maxim Rodshtein (2695)"]
  [ECO "B21"]
  [WhiteElo "2027"]
  [BlackElo "2695"]
  [PlyCount "147"]
  
  1. e4 c5 2. d4 cxd4 3. c3 d3 4. Bxd3 Nc6 5. c4 g6 6. Nf3 Bg7 7. O-O d6 8. h3 Nf6 9. Nc3 O-O 10. Be3 Nd7 11. Rc1 Nde5 12. Be2 b6 13. Qd2 Bb7 14. Rfd1 Rc8 15. b3 Nxf3+ 16. Bxf3 Ne5 17. Be2 Nd7 18. Bh6 Nf6 19. Bxg7 Kxg7 20. Bf3 Qc7 21. h4 Qb8 22. h5 Rc5 23. h6+ Kg8 24. Nd5 Bxd5 25. exd5 Rfc8 26. Re1 R8c7 27. a4 Qf8 28. Qf4 a5 29. Qe3 Kh8 30. g4 Ng8 31. g5 f6 32. gxf6 exf6 33. Qf4 Re7 34. Kf1 Re5 35. Rxe5 dxe5 36. Qd2 Qd6 37. Rd1 Rc7 38. Bg2 g5 39. Bh3 Nxh6 40. Be6 Ng8 41. Qe2 Ne7 42. Qf3 Kg7 43. Qh5 Ng6 44. Bf5 Re7 45. Rd3 Nf8 46. Rh3 Kg8 47. Be4 Rg7 48. Bf5 Re7 49. Be4 Qd7 50. Rf3 Rf7 51. Bf5 Qe7 52. Rd3 Qd6 53. Rh3 Rg7 54. Rf3 Qd8 55. Rh3 Ra7 56. Rd3 Qd6 57. Rh3 Rf7 58. Be4 Qa3 59. Bf5 Re7 60. Qd1 Qd6 61. Qd3 Rg7 62. Rh6 g4 63. Qg3 Rg5 64. Be4 Kg7 65. Qh4 Qe7 66. d6 Qf7 67. d7 Qe7 68. Rxh7+ Nxh7 69. Qxh7+ Kf8 70. Qh8+ Rg8 71. Qh6+ Rg7 72. Qh8+ Rg8 73. Qh6+ Rg7 74. Qh8+ 1/2-1/2
  
  Bd5 crying out to be played instead of Qh8.
  
  
  ---
  
  ### Answer by username_5 on 2022-01-25. Score: 2
  
  Here are two examples drawn from Fox and James, The Complete Chess Addict, pub. 1987.
  [Title "Gilberto Garcia - Borislav Ivkov, Capablanca MT 1965"]
  [fen ""]
  
  1.d4 Nf6 2.c4 e6 3.Nf3 d5 4.e3 c5
  5.dxc5 Bxc5 6.b3 O-O 7.Qc2 Nc6 8.a3 Bb6
  9.Bb2 Re8 10.Nc3 d4 11.Rd1 e5 12.e4 Ng4
  13.Na4 Ba5+ 14.b4 Nxb4 15.axb4 Bxb4+ 16.Rd2 Bd7
  17.Bc1 b5 18.Nb2 Rc8
  19.Be2 Be6 20.O-O bxc4 21.Nxc4 Qc7 22.Qa4 Bxd2 23.Bxd2 Bxc4
  24.Rc1 Qc6 25.Rxc4 Qxe4 26.Rxc8 Rxc8 27.Qd7 Rf8 28.Bf1 Nf6
  29.Qc7 Nd5 30.Qd7 Nf4 31.h3 Qb1
  32.Be1? {Best are g3/Bxf4.} e4
  33.Qf5 Ne6 34.Bd2 g6
  35.Qf6 exf3 36.g4 d3 37.Bc3 {thr Qh8#} 1-0
  
  The above game was played in round 20 of 21. After 19 rounds, Ivkov was leading, and was expected to beat the weaker Garcia and clinch first place. He lost his last two games and finished equal 4th.
  [Title "Jose Raul Capablanca - Alexander Kevitz, simul, 1924"]
  [fen ""]
  
  1.b4 d5 2.Bb2 Bf5 3.e3 e6 4.f4 Nf6
  5.Nf3 Bxb4 6.Nc3 Nbd7 7.Ne2 Ng4 8.c3 Be7
  9.h3 Nc5 {thr Nb3#}
  10.Ng3 Bh4 11.Nxh4 Qxh4 12.Qf3 Nxe3
  13.Qf2 Nxf1 {White resigned} 0-1
  
  > **Comments:**
  > **username_2**: I don't think it counts as an upset when the weaker player wins a game in a simul.  
  
  ---
  
  ### Answer by username_6 on 2012-10-08. Score: 1
  
  In a 1929 against Fritz Saemisch, a lesser master, former World Champion J. R. Capablanca blundered away a piece on the 9th move, and resigned some 50-odd moves later.
  
  <http://www.chessgames.com/perl/chessgame?gid=1066901>
  
  It was reported that Capablanca'ss wife or mistress (or possibly both) had just entered the room. In any event, the grandmaster LOST the game.
  
  > **Comments:**
  > **username_1**: Giving this as an answer to this particular question doesn't seem quite fair to Saemisch. He was no Capablanca of course, but he was one of the top players in the world for many years. Chessmetrics, for instance, puts him at #14 in 1929 (while Capablanca was #2): http://www.chessmetrics.com/cm/DL/DL80.htm. That's an upset, sure, but one between world-class players, while this question asks for examples where "a much weaker player succeeded against an IM or GM."  
  > **username_7**: Also I'm not sure he's much after piece blunders, especially if that's meant for study.  
  
  ---
  
  