Answers.Body: <p>The position is a draw, but not as easy as I first thought.</p>
  <p>At first this looks like a simple fortress for Black.</p>
  <p>Black needs to play...b5 : anyway, White can force it by bringing the wK to f4 (after c2-c3). Black has to react with ...Ke6 to prevent a trivial win on the kingside, and thus to push ...b5 to not let this pawn hanging.</p>
  <p>Then the bB holds the h7-b1 diagonal and the bK defends against wK invasions:</p>
  <ul>
  <li><p>Against wKf4, we play ...Ke6. No invasion through the kingside.</p>
  </li>
  <li><p>Against wKb4, we play ...Kc6. Instead, allowing wKc5 would soon lead to zugzwang: b5, d5 and h7 are three weaknesses, one too many for the bK and bB.</p>
  </li>
  <li><p>And just one subtelty: against wKa5 we play ...Bd3! to prevent the only possible plan for White : invasion through the a-file and the 8th-rank:</p>
  </li>
  </ul>
  <hr />
  <pre><code>[FEN &quot;8/8/2k3bP/1p1p4/1K1B4/2P2P2/8/8 w - - 0 1&quot;]
  </code></pre>
  <hr />
  <p>Now 1.Ka5!? starts the plan Ka5-a6-a7-b8-c8-d8-e8-f8-g8 ! We cannot stop the wK on c8 or e8 because of zugzwang, so we need to react now:</p>
  <p>1...Bd3! 2.Be3 Kb7! 3.Bd4 Kc6 4.Ka6? b4! (reduces the number of pawns) 5.Ka7 bc3 4.Bc3</p>
  <p>White will certainly win the Pd5 through zugzwang, but Black doesn't care : the resulting B+f,h vs B is a trivial draw.</p>
  <pre><code>[FEN &quot;8/5k1b/7P/8/3B1K2/5P2/8/8 w - - 0 1&quot;] 
  </code></pre>
  <p>Black just waits with, e.g., Bg8-h7-g8</p>
  <hr />
  <p>Edit : White can try to improve on this plan by placing her bishop on b4 and reaching this position (with Pf4 rather than Pf3) :</p>
  <hr />
  <pre><code>[FEN &quot;8/1k6/7P/Kp1p4/1B3P2/2Pb4/8/8 w - - 0 1&quot;]
  </code></pre>
  <hr />
  <p>Now:</p>
  <p>If it is White to move, he can lose a tempo by 1.Bf8 Kc6 2.Be7 Kb7 3.Bb4, since 2...Bh7 3.Ka6 progresses</p>
  <p>So let's consider it's Black's move. A bishop move loses immediately, so the two tries are 1...Kc6 holding b5 or 1...Ka7 preventing breakthrough down the a-file.</p>
  <p>I believe White has chances in both cases:</p>
  <p>1...Ka7 2.f5! is a surprising deflection that exploits the bK being so far from h7: 2...Bxf5 3.Kxb5 Kb7 4.Kc5 Be4 5.Kd6 and White wins with Kg7 and h7 - after replacing the bishop on d4 to prevent an exchange of the last pawn.</p>
  <p>1...Kc6 2.Ka6 (there is no ...b4 now) 2...Bh7 3.Ka7 Kc7 4.Ba5 Kc6 5. Kb8 Bf5 6.Bb4</p>
  <hr />
  <pre><code>[FEN &quot;1K6/8/2k4P/1p1p1b2/1B3P2/2P5/8/8 w - - 0 1&quot;]
  </code></pre>
  <hr />
  <p>Now :</p>
  <ul>
  <li><p>6...Kd7? 7.Kb7 allows the wK to c5 and leads to the loss of a pawn (and the game) by zugzwang: 7...Bh7 8.Kb6 Bd3 9.Kc5 Ke6 10.Kc6Z</p>
  </li>
  <li><p>6...Bh7? let the wK progress along the 8th rank: 7.Kc8 Bg6 8.Kd8 and the wK reaches g7, winning again.</p>
  </li>
  </ul>
  <p>In both cases White wins, yet Black still has a <strong>draw</strong> with either the passive 6...Kb6! denying any more progress for the wK, or 6...d4! 7.cd4 Kd5, aiming for counterplay. Thanks to @Scounged for checking this with Stockfish 13.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-07-09T23:11:33.190Z
Answers.Text: A few notes on the final position that may be nice to clear up: 1) What happens if Black plays 6...Kb6? How does white break through then? 2) How does white handle a "desperado" play with something like 6...d4 (or this exact pawn sac down the line)? If 6...d4 7.cxd4 Kd5 white has to give the pawn on d4, and I'm not sure whether it's easy to prevent black from reaching a fortress there. 3) What happens if black tries to combine ideas from 1 and 2? If white has to sac the h-pawn to deal with point 1, then point 2 will make it very hard to win.
Answers.UserDisplayName: Scounged
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-07-10T16:56:22.057Z
Answers.Text: I'd like to add to my previous comment: in the final position, Stockfish 13 has confirmed that the position is indeed drawn after 6...d4! After analyzing with the computer I think that 6...Kb6 also draws, although it's interesting to note that the computer doesn't understand that it can't make any progress.
Answers.UserDisplayName: Scounged
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-08-21T14:03:11.277Z
Answers.Text: @Scounged thanks, both moves make a lot of sense. I edited them into my answer and re-revised my evaluation accordingly.
Answers.UserDisplayName: Evargalo
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-07-05T09:34:05.433Z
Answers.LastActivityDate: 2022-08-21T14:01:57.527Z
Answers.LastEditDate: 2022-08-21T14:01:57.527Z
Answers.UserDisplayName: Evargalo
Answers.Body: <p>According to Stockfish 14.1 NNUE White Wins with C3, though it IS very complicated and it IS necessary to go to depth =. 79 or higher to get it.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-06-03T19:15:08.607Z
Answers.LastActivityDate: 2022-06-03T19:15:08.607Z
Answers.UserDisplayName: Stefano
Answers.Body: <p>According to Stockfish 14.1 NNUE depth =90 the position is evaluated at 4.25, that appears to be a win, yet it may be necessary FinalGen to get a definitive answer.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-08-19T19:32:47.943Z
Answers.LastActivityDate: 2022-08-19T19:32:47.943Z
Answers.UserDisplayName: Stefano
Answers.Body: <p>After long analysis, it seems that Black defense could be broken. But more than 50 moves without pawn moves or captures are necessary at a certain point. With still 8 pieces on the board , and therefore a draw under both FIDE and ICCF rules , though it is not a technical draw.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-07-05T08:49:47.623Z
Answers.Text: Self-answers are ok on C.SE, but for this one to be valuable you need to include at least a main line. Softwares' evaluations are not very interesting by themselves.
Answers.UserDisplayName: Evargalo
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-07-08T12:03:52.223Z
Answers.Text: "_...Black's defense could be broken_."  How?  What is the principal variation?
Answers.UserDisplayName: SecretAgentMan
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-07-03T16:18:43.823Z
Answers.LastActivityDate: 2021-07-05T16:29:19.657Z
Answers.LastEditDate: 2021-07-05T16:29:19.657Z
Answers.UserDisplayName: user27314
Answers.Body: <p>Based on the answer of Evargalo, who demonstrates nicely a critical attack line to storm the fortress.
  Following the bishop on b4 line at &quot;1...Kc6 2.Ka6 (there is no ...b4 now) 2...Bh7 3.Ka7 Kc7 4.Ba5&quot; Black can deviate, counterattacking and modifying to a smaller fortress, with a line like Kd6 5. Kb6 Ke6 6. Kxb5 Kf5 7. Bc7 Kg6 8. Kc6 Bg8 9. Kd6 Kxh6 10. f5 Kg5 11. Ke5 Bh7 12. Bd8+ Kg4 13. f6 Bg8 14. Kd6 Kf5 15. Ke7 Kg6 drawing.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-07-09T22:20:13.877Z
Answers.LastActivityDate: 2021-07-09T22:20:13.877Z
Answers.UserDisplayName: eaglewing
Body: <p>This endgame may even be critical of the entire variation. Stockfish 13 on move 34 depth 70/94 11.3 M of six men tablebases suggest a line that lead to the following endgame.</p>
  <pre><code>[FEN &quot;8/2k5/1p4bP/3p4/8/4B3/1KP2P2/8 w - - 0 1&quot;]
  </code></pre>
  <p>I tried with Houdini 6.02 and it give a fixed score of 1.49 , but on the second iteration ( after lot of depth and lot of moves) evaluation  started going up. It suggest a deep win , but is really true? After all , Black may have a better defense, or may be able to reach the 50 move rule. What happens with perfect play? I suspect only Stockfish 13 running on DruDru technology on depth 70 ( or even higher!)with 7 men tablebases is able to give a definite answer.</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-07-02T12:49:26.697Z
Comments.Text: There are many subvariations of the Winawer french, and I cannot imagine for a second that this endgame (which seems to have taken more than 40 moves to reach) would be critical to the evaluation of the entire variation.
Comments.UserDisplayName: Scounged
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-07-05T08:53:10.890Z
Comments.Text: Notwithstandaing the verdict about this position, I am certain it will not be the final word about the Winawer French. It looks very drawish to me, but before we delve into variations, please give us some useful information, like: whose move is it ?
Comments.UserDisplayName: Evargalo
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-07-11T00:21:10.240Z
Comments.Text: So what *is* the critical Winawer line that leads to this ending?
Comments.UserDisplayName: Noam D. Elkies
Tags: <endgame><computer-chess>
Title: A critical endgame in the French Winaver
ThreadText: # A critical endgame in the French Winaver
  
  (Asked by: username_0 on 2021-06-30)
  
  This endgame may even be critical of the entire variation. Stockfish 13 on move 34 depth 70/94 11.3 M of six men tablebases suggest a line that lead to the following endgame.
  [FEN "8/2k5/1p4bP/3p4/8/4B3/1KP2P2/8 w - - 0 1"]
  
  I tried with Houdini 6.02 and it give a fixed score of 1.49 , but on the second iteration ( after lot of depth and lot of moves) evaluation  started going up. It suggest a deep win , but is really true? After all , Black may have a better defense, or may be able to reach the 50 move rule. What happens with perfect play? I suspect only Stockfish 13 running on DruDru technology on depth 70 ( or even higher!)with 7 men tablebases is able to give a definite answer.
  
  **Tags:** endgame, computer-chess
  
  > **Comments:**
  > **username_1**: There are many subvariations of the Winawer french, and I cannot imagine for a second that this endgame (which seems to have taken more than 40 moves to reach) would be critical to the evaluation of the entire variation.  
  > **username_2**: Notwithstandaing the verdict about this position, I am certain it will not be the final word about the Winawer French. It looks very drawish to me, but before we delve into variations, please give us some useful information, like: whose move is it ?  
  > **username_3**: So what *is* the critical Winawer line that leads to this ending?  
  
  ---
  
  ## 5 answers
  
  ### Answer by username_2 on 2021-07-05. Score: 4
  
  The position is a draw, but not as easy as I first thought.
  At first this looks like a simple fortress for Black.
  Black needs to play...b5 : anyway, White can force it by bringing the wK to f4 (after c2-c3). Black has to react with ...Ke6 to prevent a trivial win on the kingside, and thus to push ...b5 to not let this pawn hanging.
  Then the bB holds the h7-b1 diagonal and the bK defends against wK invasions:
  
  Against wKf4, we play ...Ke6. No invasion through the kingside.
  
  Against wKb4, we play ...Kc6. Instead, allowing wKc5 would soon lead to zugzwang: b5, d5 and h7 are three weaknesses, one too many for the bK and bB.
  
  And just one subtelty: against wKa5 we play ...Bd3! to prevent the only possible plan for White : invasion through the a-file and the 8th-rank:
  
  
  
  [FEN "8/8/2k3bP/1p1p4/1K1B4/2P2P2/8/8 w - - 0 1"]
  
  
  Now 1.Ka5!? starts the plan Ka5-a6-a7-b8-c8-d8-e8-f8-g8 ! We cannot stop the wK on c8 or e8 because of zugzwang, so we need to react now:
  1...Bd3! 2.Be3 Kb7! 3.Bd4 Kc6 4.Ka6? b4! (reduces the number of pawns) 5.Ka7 bc3 4.Bc3
  White will certainly win the Pd5 through zugzwang, but Black doesn't care : the resulting B+f,h vs B is a trivial draw.
  [FEN "8/5k1b/7P/8/3B1K2/5P2/8/8 w - - 0 1"] 
  
  Black just waits with, e.g., Bg8-h7-g8
  
  Edit : White can try to improve on this plan by placing her bishop on b4 and reaching this position (with Pf4 rather than Pf3) :
  
  [FEN "8/1k6/7P/Kp1p4/1B3P2/2Pb4/8/8 w - - 0 1"]
  
  
  Now:
  If it is White to move, he can lose a tempo by 1.Bf8 Kc6 2.Be7 Kb7 3.Bb4, since 2...Bh7 3.Ka6 progresses
  So let's consider it's Black's move. A bishop move loses immediately, so the two tries are 1...Kc6 holding b5 or 1...Ka7 preventing breakthrough down the a-file.
  I believe White has chances in both cases:
  1...Ka7 2.f5! is a surprising deflection that exploits the bK being so far from h7: 2...Bxf5 3.Kxb5 Kb7 4.Kc5 Be4 5.Kd6 and White wins with Kg7 and h7 - after replacing the bishop on d4 to prevent an exchange of the last pawn.
  1...Kc6 2.Ka6 (there is no ...b4 now) 2...Bh7 3.Ka7 Kc7 4.Ba5 Kc6 5. Kb8 Bf5 6.Bb4
  
  [FEN "1K6/8/2k4P/1p1p1b2/1B3P2/2P5/8/8 w - - 0 1"]
  
  
  Now :
  
  6...Kd7? 7.Kb7 allows the wK to c5 and leads to the loss of a pawn (and the game) by zugzwang: 7...Bh7 8.Kb6 Bd3 9.Kc5 Ke6 10.Kc6Z
  
  6...Bh7? let the wK progress along the 8th rank: 7.Kc8 Bg6 8.Kd8 and the wK reaches g7, winning again.
  
  
  In both cases White wins, yet Black still has a draw with either the passive 6...Kb6! denying any more progress for the wK, or 6...d4! 7.cd4 Kd5, aiming for counterplay. Thanks to @username_1 for checking this with Stockfish 13.
  
  > **Comments:**
  > **username_1**: A few notes on the final position that may be nice to clear up: 1) What happens if Black plays 6...Kb6? How does white break through then? 2) How does white handle a "desperado" play with something like 6...d4 (or this exact pawn sac down the line)? If 6...d4 7.cxd4 Kd5 white has to give the pawn on d4, and I'm not sure whether it's easy to prevent black from reaching a fortress there. 3) What happens if black tries to combine ideas from 1 and 2? If white has to sac the h-pawn to deal with point 1, then point 2 will make it very hard to win.  
  > **username_1**: I'd like to add to my previous comment: in the final position, Stockfish 13 has confirmed that the position is indeed drawn after 6...d4! After analyzing with the computer I think that 6...Kb6 also draws, although it's interesting to note that the computer doesn't understand that it can't make any progress.  
  > **username_2**: @username_1 thanks, both moves make a lot of sense. I edited them into my answer and re-revised my evaluation accordingly.  
  
  ---
  
  ### Answer by username_4 on 2022-06-03. Score: 1
  
  According to Stockfish 14.1 NNUE White Wins with C3, though it IS very complicated and it IS necessary to go to depth =. 79 or higher to get it.
  
  
  ---
  
  ### Answer by username_4 on 2022-08-19. Score: 0
  
  According to Stockfish 14.1 NNUE depth =90 the position is evaluated at 4.25, that appears to be a win, yet it may be necessary FinalGen to get a definitive answer.
  
  
  ---
  
  ### Answer by username_6 on 2021-07-09. Score: 0
  
  Based on the answer of username_2, who demonstrates nicely a critical attack line to storm the fortress.
  Following the bishop on b4 line at "1...Kc6 2.Ka6 (there is no ...b4 now) 2...Bh7 3.Ka7 Kc7 4.Ba5" Black can deviate, counterattacking and modifying to a smaller fortress, with a line like Kd6 5. Kb6 Ke6 6. Kxb5 Kf5 7. Bc7 Kg6 8. Kc6 Bg8 9. Kd6 Kxh6 10. f5 Kg5 11. Ke5 Bh7 12. Bd8+ Kg4 13. f6 Bg8 14. Kd6 Kf5 15. Ke7 Kg6 drawing.
  
  
  ---
  
  ### Answer by username_0 on 2021-07-03. Score: -3
  
  After long analysis, it seems that Black defense could be broken. But more than 50 moves without pawn moves or captures are necessary at a certain point. With still 8 pieces on the board , and therefore a draw under both FIDE and ICCF rules , though it is not a technical draw.
  
  > **Comments:**
  > **username_2**: Self-answers are ok on C.SE, but for this one to be valuable you need to include at least a main line. Softwares' evaluations are not very interesting by themselves.  
  > **username_5**: "_...Black's defense could be broken_."  How?  What is the principal variation?  
  
  ---
  
  