Answers.Body: <p>The position is very advantageous for Black anyway, but there are two points in including 14...c4 15.dc4 before sacrificing the knight:</p>
  <ul>
  <li><p>Deflecting the wPd3 give access to e4 to Black pieces if White plays fg4. Especially the Bg6 will gladly join the mating attack.</p>
  </li>
  <li><p>Since Black Pd5 will be undefended after the knight departure, it is worth preventing any Bxd5 by White : the bishop there would be excellently placed in the center, defending h1/g2/f3 on one diagonal and attacking f7 on the other. A White pawn on d5 (after a possible cxd5) will be much less annoying, threatening nothing and blocking the Bb3.</p>
  </li>
  <li><p>At any moment, Black can drag the white Bishop to the unprotected square c4, where it might become a target to horizontal attacks by the queen. E.g., if 14...c4 15.dc4 Nxg4 16.fg4 Qh4 17.Kf1 Qh3 [simply 17...Be4 must already be winning] 18.Kf2 Qh2 19.Kf1, then 19...dc4 20.Bxc4 Qh3 21.Kf2 Qxg4 is a pattern to take into account even if it also exposes the Bd6 on the d-file.</p>
  </li>
  </ul>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-10-19T07:38:05.320Z
Answers.Text: Just nitpicking and desparately trying to analyze in my head (I can't), but White must stay on f1 with the king since Kf3 Be4+ is mate immediately?! BTW, this underlines an advantage of c4 you didn't mention yet - Pd3 is deflected and the other bishop can join the fray by Be4.
Answers.UserDisplayName: Hauke Reddmann
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-10-19T13:16:05.693Z
Answers.Text: @HaukeReddmann you are right. It seems I can't calculate in my head either. I edit the answer.
Answers.UserDisplayName: Evargalo
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-10-20T08:12:55.480Z
Answers.Text: I felt free to also swap "Black" and "White" in the added paragraph. ("Fischers theorem" - no, not Bobby, but Emil, chemistry nobel. As my prof always quoted him, bugs preferrably sit in the last minute edits, much less in main text.)
Answers.UserDisplayName: Hauke Reddmann
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-10-19T07:17:20.933Z
Answers.LastActivityDate: 2021-10-20T08:08:46.063Z
Answers.LastEditDate: 2021-10-20T08:08:46.063Z
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Body: <pre><code>[FEN &quot;rn2r1k1/pp2qpp1/3b1nbp/2pp4/6PP/1B1PBP2/PPPQNK2/RN2R3 b KQkq - 0 14&quot;]
  </code></pre>
  <p>14... c4 15. dxc4 Nxg4+</p>
  <p>I set up the above position in Stockfish and the initial analysis was that <code>c4</code> was the best move. After some time it changed its evaluation and gave <code>Nc6</code></p>
  <p>I am trying to understand the idea behind the continuation <code>C4</code>, It looks like a pawn loss and a waste of tempo, If the plan is to sacrifice the Knight, why not just sacrifice it at move 14?(move 1 in the above position?) instead of wasting the pawn then &quot;sac&quot; the Knight?</p>
  
Tags: <analysis><strategy><sacrifice>
Title: How is c4 the best move in this position?
ThreadText: # How is c4 the best move in this position?
  
  (Asked by: username_0 on 2021-10-19)
  
  [FEN "rn2r1k1/pp2qpp1/3b1nbp/2pp4/6PP/1B1PBP2/PPPQNK2/RN2R3 b KQkq - 0 14"]
  
  14... c4 15. dxc4 Nxg4+
  I set up the above position in Stockfish and the initial analysis was that c4 was the best move. After some time it changed its evaluation and gave Nc6
  I am trying to understand the idea behind the continuation C4, It looks like a pawn loss and a waste of tempo, If the plan is to sacrifice the Knight, why not just sacrifice it at move 14?(move 1 in the above position?) instead of wasting the pawn then "sac" the Knight?
  
  **Tags:** analysis, strategy, sacrifice
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2021-10-19. Score: 4
  
  The position is very advantageous for Black anyway, but there are two points in including 14...c4 15.dc4 before sacrificing the knight:
  
  * Deflecting the wPd3 give access to e4 to Black pieces if White plays fg4. Especially the Bg6 will gladly join the mating attack.
  * Since Black Pd5 will be undefended after the knight departure, it is worth preventing any Bxd5 by White : the bishop there would be excellently placed in the center, defending h1/g2/f3 on one diagonal and attacking f7 on the other. A White pawn on d5 (after a possible cxd5) will be much less annoying, threatening nothing and blocking the Bb3.
  * At any moment, Black can drag the white Bishop to the unprotected square c4, where it might become a target to horizontal attacks by the queen. E.g., if 14...c4 15.dc4 Nxg4 16.fg4 Qh4 17.Kf1 Qh3 [simply 17...Be4 must already be winning] 18.Kf2 Qh2 19.Kf1, then 19...dc4 20.Bxc4 Qh3 21.Kf2 Qxg4 is a pattern to take into account even if it also exposes the Bd6 on the d-file.
  
  > **Comments:**
  > **username_2**: Just nitpicking and desparately trying to analyze in my head (I can't), but White must stay on f1 with the king since Kf3 Be4+ is mate immediately?! BTW, this underlines an advantage of c4 you didn't mention yet - Pd3 is deflected and the other bishop can join the fray by Be4.  
  > **username_1**: @HaukeReddmann you are right. It seems I can't calculate in my head either. I edit the answer.  
  > **username_2**: I felt free to also swap "Black" and "White" in the added paragraph. ("Fischers theorem" - no, not Bobby, but Emil, chemistry nobel. As my prof always quoted him, bugs preferrably sit in the last minute edits, much less in main text.)  
  
  ---
  
  