Answers.Body: <p>I doubt very much that you can find anything that is both obvious (to the human eye) and new and strong, but a good candidate for the most drastically re-evaluated simple move might be 3..Nf6 against the Lopez.</p>
  
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Answers.CreationDate: 2017-08-17T16:44:35.657Z
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Answers.UserDisplayName: Philip Roe
Answers.Body: <p>There are thousands of small evaluation changes, but there's only a few complete turnarounds busting main lines considered good for decades. Two examples come to my mind. First is correspondence game Voss-Zhak 2010, 30.Re6 winning, refuting the old main line of moscow gambit. Also 22.Kf1 from Giri-Shirov 2014 (found earlier in correspondence games) made old main line Sveshnikov almost lost for black. Both these recent games changed theory evaluations seriously.</p>
  
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Answers.CreationDate: 2017-08-18T11:45:32.843Z
Answers.Text: Interesting, but by moves 22 and 30 I am not sure we're in the opening phase of the game.
Answers.UserDisplayName: Tony Ennis
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Answers.Text: @TonyEnnis The question was not about moves in the opening, but about moves (at any point during a game) that change the evaluation of an opening position. Also at GM level, moves 22 and 30 can well be considered opening phase in some lines.
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Answers.Text: "Opening lines" is in the title.
Answers.UserDisplayName: Tony Ennis
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Answers.CreationDate: 2017-08-19T08:39:02.693Z
Answers.Text: How about 26.Re7+ in the Vaisser-Bauer game? Isn't White winning then?
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Answers.UserDisplayName: hoacin
Body: <p>What is the most obvious move, (or simple sequence of moves) long overlooked by opening theory in the last 50 years or so, completely changing the evaluation of a well-known position? </p>
  
  <p>EDIT: Well, I mean those cases in which "an unknown amateur from Siberia wrote to the famous chess magazine that White is losing, because after the simple 12...Nxc3, White cannot take back, because of the discovered check..." Are those just urban legends, or they did actually happen? I am curious...</p>
  
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Comments.CreationDate: 2017-08-17T13:04:11.650Z
Comments.Text: This question is very broad and will probably be closed if it isn't edited.
Comments.UserDisplayName: Aric
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Comments.Text: There are too many to list.  Just listing the computer's breakthroughs would take pages.
Comments.UserDisplayName: Fred Knight
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Comments.CreationDate: 2017-08-17T23:14:14.447Z
Comments.Text: We have had GMs of incredible strength for 100+ years. There are no simple overlooked moves in the opening phases of the game.
Comments.UserDisplayName: Tony Ennis
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Comments.CreationDate: 2017-08-18T02:27:53.683Z
Comments.Text: @TonyEnnis No doubt there are no simple overlooked moves in the main line openings that those incredibly strong GMs have been playing for the past 100 years, but maybe in some obscure variation of the Steinitz Gambit or the Anderssen Counterattack?
Comments.UserDisplayName: bof
Tags: <opening><theory>
Title: Opening theory overlooking simple moves?
ThreadText: # Opening theory overlooking simple moves?
  
  (Asked by: username_0 on 2017-08-17)
  
  What is the most obvious move, (or simple sequence of moves) long overlooked by opening theory in the last 50 years or so, completely changing the evaluation of a well-known position?
  
  EDIT: Well, I mean those cases in which "an unknown amateur from Siberia wrote to the famous chess magazine that White is losing, because after the simple 12...Nxc3, White cannot take back, because of the discovered check..." Are those just urban legends, or they did actually happen? I am curious...
  
  **Tags:** opening, theory
  
  > **Comments:**
  > **username_1**: This question is very broad and will probably be closed if it isn't edited.  
  > **username_2**: There are too many to list.  Just listing the computer's breakthroughs would take pages.  
  > **username_3**: We have had GMs of incredible strength for 100+ years. There are no simple overlooked moves in the opening phases of the game.  
  > **username_4**: @username_3 No doubt there are no simple overlooked moves in the main line openings that those incredibly strong GMs have been playing for the past 100 years, but maybe in some obscure variation of the Steinitz Gambit or the Anderssen Counterattack?  
  
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  ## 2 answers
  
  ### Answer by username_5 on 2017-08-17. Score: 3
  
  I doubt very much that you can find anything that is both obvious (to the human eye) and new and strong, but a good candidate for the most drastically re-evaluated simple move might be 3..Nf6 against the Lopez.
  
  
  ---
  
  ### Answer by username_6 on 2017-08-17. Score: 2
  
  There are thousands of small evaluation changes, but there's only a few complete turnarounds busting main lines considered good for decades. Two examples come to my mind. First is correspondence game Voss-Zhak 2010, 30.Re6 winning, refuting the old main line of moscow gambit. Also 22.Kf1 from Giri-Shirov 2014 (found earlier in correspondence games) made old main line Sveshnikov almost lost for black. Both these recent games changed theory evaluations seriously.
  
  > **Comments:**
  > **username_3**: Interesting, but by moves 22 and 30 I am not sure we're in the opening phase of the game.  
  > **username_7**: @username_3 The question was not about moves in the opening, but about moves (at any point during a game) that change the evaluation of an opening position. Also at GM level, moves 22 and 30 can well be considered opening phase in some lines.  
  > **username_3**: "Opening lines" is in the title.  
  > **username_0**: How about 26.Re7+ in the Vaisser-Bauer game? Isn't White winning then?  
  
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