Answers.Body: <p>From a purely positional point of view, <code>18...Nxb6</code> would have been a
  terrible mistake, as it would have allowed white to then forcefully trade the light squared bishops with the immediate <code>Bg4</code>
  move, leaving <em>exposed</em> all the <em>light square</em> weaknesses that black has
  created with the <code>d6-e5-f4</code> setup.</p>
  
  <p>These weaknesses (created holes) would then have been permanently exploited by white's
  knight (and queen), in other words, white's minor piece (<code>b6</code> knight) would have
  dominated the game and been virtually untouchable on light squares for the rest of the game.
  Notice that next to the knight controlling key light squares from <code>b6</code>,
  it's also for example quite feasible for white to re-route the knight
  to <code>e4,</code> established centrally (permanently) and constantly eying black's
  weak <code>d6</code> pawn.</p>
  
  <p>And as for black, Carlsen would have simply been left with a bad dark
  squared bishop <em>hemmed in</em> by his <em>own structure</em>.
  Therefore, Carlsen chose wisely to play <code>Qe8</code> instead of <code>Nxb6</code>, thus,
  preserving his <code>c8</code> bishop as <code>Bg4</code> no longer forces a trade thanks to
  the well placed knight on <code>d7.</code></p>
  
  <p>In summary, this is a purely positional decision where black is well
  aware that having weakened their light squares, any scenario with the
  <strong>knight vs dark square bishop</strong> would be unfavorable for them, and
  arguably,
  at that level even objectively lost! Instead having kept both the <code>d7</code>
  knight and <code>c8</code> bishop, black has in fact preserved two pieces that can
  provide light square control.</p>
  
  <p>The following situations would have ensued had Carlsen played
  <code>18...Nxb6</code>:</p>
  
  <p><code>18...Nxb6 19.Nxb6 Ra7 20.Bg4</code></p>
  
  <p><a href="https://i.sstatic.net/ePklGb.png" rel="noreferrer"><img src="https://i.sstatic.net/ePklGb.png" alt="enter image description here"></a></p>
  
  <p>which would have led to positions of the following nature, infested with light square holes:</p>
  
  <p><a href="https://i.sstatic.net/ruCZ0b.png" rel="noreferrer"><img src="https://i.sstatic.net/ruCZ0b.png" alt="enter image description here"></a></p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-02-28T17:16:19.207Z
Answers.Text: Speaking of game 10, I just found you a **gem**: https://www.youtube.com/watch?v=ctiw40M-Fo4 A **complete analysis** of the game by none other than Peter Svidler!
Answers.UserDisplayName: Ellie
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-02-28T16:50:32.007Z
Answers.LastActivityDate: 2019-02-28T16:50:32.007Z
Answers.UserDisplayName: Ellie
Answers.Body: <p>After 18 ... Qe8 the bishop on b6 is attacking thin air and isn't very annoying.<br>
  After 18 ... Nxb6 19. Nxb6 the knight on b6 is very annoying indeed. The a8 rook is forced to a7 and black's pieces are becoming uncoordinated.<br>
  After 18 ... Nxb6 19. axb6 Rxa1 20. Qxa1 black is in trouble. White's b6 pawn is looking dangerous, black's b7 pawn is going to come under attack and his position is cramped and uncoordinated.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-02-28T16:51:17.817Z
Answers.LastActivityDate: 2019-02-28T16:51:17.817Z
Answers.UserDisplayName: Brian Towers
Answers.Body: <p>Several reasons I can think of:</p>
  
  <ul>
  <li>black is obviously playing on the kingside and <strong>Qe8 is a useful move</strong> aiming to transfer the queen to f7, g6 or perhaps h5 later. Also it might be useful to push e4 later.</li>
  <li>the bishop on b6 <strong>is not annoying</strong>. At the moment it attacks the black queen but that's about it. To some extent it is also blocking other white pieces. Also the bishop does not have many squares and could (if necessary) be taken later.</li>
  <li>the position after 18...Nxb6 19 Nxb6 is worse, because now you have a knight on b6 and the pawn on b7 is more prone to become weak. Also the light squares are much weaker then.</li>
  </ul>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-02-28T16:43:52.623Z
Answers.LastActivityDate: 2019-02-28T16:43:52.623Z
Answers.UserDisplayName: user1583209
Body: <p>In game 10 of the Caruana-Carlsen WCC, why did Carlsen (black) not take the terribly annoying and strong dark squared bishop on <code>b6</code> on move 18 when given the chance? Instead, Carlsen moved the queen with <code>Qe8.</code></p>
  
  <p>The position is shown in the following diagram:</p>
  
  <pre><code> [title "Caruana vs Carlsen, game 10, why not 18...Nxb6 instead of 18...Qe8"]
   [fen "r1bq1rk1/1p1nb1pp/1B1p4/P2Pp3/2N2p2/8/2P1BPPP/R2Q1RK1 b - - 0 1"]
  </code></pre>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2019-02-28T17:39:17.957Z
Comments.Text: What makes you think the Bishop "terribly annoying and strong"?  It has hardly any squares!
Comments.UserDisplayName: Ywapom
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2019-02-28T20:53:40.067Z
Comments.Text: @Ywapom admittedly that was a bit of an overstatement, I just mean the bishop's doing quite a good job at pinning down dark squares on the queenside without being under any threat and is ready to move to c7 coordinating with the knight to target black's most important weak pawn (backbone of e5-f4).  Which all in all makes it into a decent minor piece at least compared to black bishop on e7.
Comments.UserDisplayName: user929304
Tags: <strategy><world-championship><carlsen>
Title: Caruana vs Carlsen game 10 (WCC) why not 18...Nxb6?
ThreadText: # Caruana vs Carlsen game 10 (WCC) why not 18...Nxb6?
  
  (Asked by: username_0 on 2019-02-28)
  
  In game 10 of the Caruana-Carlsen WCC, why did Carlsen (black) not take the terribly annoying and strong dark squared bishop on b6 on move 18 when given the chance? Instead, Carlsen moved the queen with Qe8.
  The position is shown in the following diagram:
   [title "Caruana vs Carlsen, game 10, why not 18...Nxb6 instead of 18...Qe8"]
   [fen "r1bq1rk1/1p1nb1pp/1B1p4/P2Pp3/2N2p2/8/2P1BPPP/R2Q1RK1 b - - 0 1"]
  
  **Tags:** strategy, world-championship, carlsen
  
  > **Comments:**
  > **username_1**: What makes you think the Bishop "terribly annoying and strong"?  It has hardly any squares!  
  > **username_0**: @username_1 admittedly that was a bit of an overstatement, I just mean the bishop's doing quite a good job at pinning down dark squares on the queenside without being under any threat and is ready to move to c7 coordinating with the knight to target black's most important weak pawn (backbone of e5-f4).  Which all in all makes it into a decent minor piece at least compared to black bishop on e7.  
  
  ---
  
  ## 3 answers
  
  ### Answer by username_2 on 2019-02-28. Score: 14
  
  From a purely positional point of view, `18...Nxb6` would have been a
  terrible mistake, as it would have allowed white to then forcefully trade the light squared bishops with the immediate `Bg4`
  move, leaving *exposed* all the *light square* weaknesses that black has
  created with the `d6-e5-f4` setup.
  
  These weaknesses (created holes) would then have been permanently exploited by white's
  knight (and queen), in other words, white's minor piece (`b6` knight) would have
  dominated the game and been virtually untouchable on light squares for the rest of the game.
  Notice that next to the knight controlling key light squares from `b6`,
  it's also for example quite feasible for white to re-route the knight
  to `e4,` established centrally (permanently) and constantly eying black's
  weak `d6` pawn.
  
  And as for black, Carlsen would have simply been left with a bad dark
  squared bishop *hemmed in* by his *own structure*.
  Therefore, Carlsen chose wisely to play `Qe8` instead of `Nxb6`, thus,
  preserving his `c8` bishop as `Bg4` no longer forces a trade thanks to
  the well placed knight on `d7.`
  
  In summary, this is a purely positional decision where black is well
  aware that having weakened their light squares, any scenario with the
  **knight vs dark square bishop** would be unfavorable for them, and
  arguably,
  at that level even objectively lost! Instead having kept both the `d7`
  knight and `c8` bishop, black has in fact preserved two pieces that can
  provide light square control.
  
  The following situations would have ensued had Carlsen played
  `18...Nxb6`:
  
  `18...Nxb6 19.Nxb6 Ra7 20.Bg4`
  
  [![enter image description here](https://i.sstatic.net/ePklGb.png)](https://i.sstatic.net/ePklGb.png)
  
  which would have led to positions of the following nature, infested with light square holes:
  
  [![enter image description here](https://i.sstatic.net/ruCZ0b.png)](https://i.sstatic.net/ruCZ0b.png)
  
  > **Comments:**
  > **username_2**: Speaking of game 10, I just found you a **gem**: https://www.youtube.com/watch?v=ctiw40M-Fo4 A **complete analysis** of the game by none other than Peter Svidler!  
  
  ---
  
  ### Answer by username_3 on 2019-02-28. Score: 11
  
  After 18 ... Qe8 the bishop on b6 is attacking thin air and isn't very annoying.  
  After 18 ... Nxb6 19. Nxb6 the knight on b6 is very annoying indeed. The a8 rook is forced to a7 and black's pieces are becoming uncoordinated.  
  After 18 ... Nxb6 19. axb6 Rxa1 20. Qxa1 black is in trouble. White's b6 pawn is looking dangerous, black's b7 pawn is going to come under attack and his position is cramped and uncoordinated.
  
  
  ---
  
  ### Answer by username_4 on 2019-02-28. Score: 10
  
  Several reasons I can think of:
  
  * black is obviously playing on the kingside and **Qe8 is a useful move** aiming to transfer the queen to f7, g6 or perhaps h5 later. Also it might be useful to push e4 later.
  * the bishop on b6 **is not annoying**. At the moment it attacks the black queen but that's about it. To some extent it is also blocking other white pieces. Also the bishop does not have many squares and could (if necessary) be taken later.
  * the position after 18...Nxb6 19 Nxb6 is worse, because now you have a knight on b6 and the pawn on b7 is more prone to become weak. Also the light squares are much weaker then.
  
  
  ---
  
  