Answers.Body: <p><em>This answer does not use modern analysis.</em></p>
  
  <p>One can always consult the old masters for advice.</p>
  
  <p>One of the first epic rivalries in chess was between an Irishman and a Frenchman: Alexander McDonnell and Louis Charles Mahé de la Bourdonnais. In the course of their six-match slugfest in 1834, this opening line arose thrice, with de la Bourdonnais taking 2 points out of 3 from the black side. What did he do?</p>
  
  <p>All three games went <code>1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 e5 5. Nxc6?! bxc6</code>, a surprisingly modern opening.</p>
  
  <p>In <a href="https://www.chessgames.com/perl/chessgame?gid=1001160" rel="nofollow noreferrer">this game</a>, de la Bourdonnais' control of d5 and d6 was solid enough that he could forgo castling, play ...Ke7, and barrel down the kingside. Black had some attacking potential while white could not break through in the centre because the c6-pawn guarded d5 and b5; black's attack eventually petered out and he managed to hold a draw against white's slow queenside attack.</p>
  
  <pre><code>[Event "London"]
  [Date "1834"]
  [Result "0-1"]
  [White "Alexander McDonnell"]
  [Black "Louis Charles Mahe De La Bourdonnais"]
  [FEN ""]
  
  1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 e5 5.Nxc6 bxc6 6.Bc4 Nf6 7.Bg5 Bc5 8.O-O h6 9.Bxf6 Qxf6 10.Nc3 a5 11.Kh1 d6 12.Qd2 g5 13.Rad1 Ke7 14.Na4 Bd4 15.Qd3 h5 16.Qb3 h4 17.f3 h3 18.g3 Bd7 19.c3 Rab8 20.Qc2 Ba7 21.Qd2 Rhg8 22.b3 Rbd8 23.Nb2 Rg7 24.Be2 Qg6 25.Nc4 Bc5 26.Nxa5 Rb8 27.b4 Bb6 28.Nc4 Qf6 29.Nxd6 Rgg8 30.Nxf7 Be6 31.Nd6 Rgd8 32.c4 Bxc4 33.Bxc4 Rxd6 34.Qxd6+ Qxd6 35.Rxd6 Kxd6 36.Rb1 Bd4 37.Bf1 Ra8 38.Bxh3 Rxa2 39.Bg2 Rb2 40.Rxb2 Bxb2 41.Bf1 Ke6 42.Kg2 Kf6 43.Kh3 Bc3 44.b5 cxb5 45.Bxb5 Bd4 46.Kg4 Be3 47.h4 gxh4 48.Kxh4 Bc5 49.Kg4 Bf2 50.f4 Bd4 51.Kf3 Bc3 52.Kg4 Bd4 53.Kh5 Bf2 54.Kg4 Bd4 55.Bd3 Be3 56.Kf3 Bd2 1/2-1/2
  </code></pre>
  
  <p>The <a href="https://www.chessgames.com/perl/chessgame?gid=1001164" rel="nofollow noreferrer">next example</a> is a little different; early tactics saw mass exchanges down the e-file and yielded an entirely different sort of game, which again ended up drawn. Instead of <code>9...Nxe4</code> (which yields equality anyway), black could have tried other options to achieve the usual plan of ...d5 in the Sicilian. (Although in 1834, it was not "usual" in the slightest...)</p>
  
  <pre><code>[Event "London"]
  [Date "1834"]
  [Result "0-1"]
  [White "Alexander McDonnell"]
  [Black "Louis Charles Mahe De La Bourdonnais"]
  [FEN ""]
  
  1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 e5 5.Nxc6 bxc6 6.Bc4 Nf6 7.Qe2 Be7 8.Nc3 O-O 9.Bg5 Nxe4 10.Bxe7 Nxc3 11.Qxe5 Re8 12.O-O Qxe7 13.Qxc3 d5 14.Bd3 Qd6 15.Rad1 Bd7 16.Qd4 c5 17.Qh4 g6 18.c3 Bc6 19.f4 c4 20.Bb1 Re2 21.Rf2 Rae8 22.f5 Qe5 23.Rdf1 Qe3 24.fxg6 fxg6 25.Qf6 Rxf2 26.Qxf2 Kg7 27.Qxe3 Rxe3 28.Kf2 Re5 29.Re1 Rxe1 30.Kxe1 1/2-1/2
  </code></pre>
  
  <p>And for those who know the classics, <a href="https://www.chessgames.com/perl/chessgame?gid=1001165" rel="nofollow noreferrer">this game is the one you've been waiting for since starting to read this answer</a>. It is downright famous, and everyone should take a look. It is said that the problem with <code>5. Nxc6?!</code> is in allowing black to strengthen the centre with more pawns -- and just look at the final position for the culmination of that strategy.</p>
  
  <pre><code>[Event "London"]
  [Date "1834"]
  [Result "0-1"]
  [White "Alexander McDonnell"]
  [Black "Louis Charles Mahe De La Bourdonnais"]
  [FEN ""]
  
  1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 e5 5.Nxc6 bxc6 6.Bc4 Nf6 7.Bg5 Be7 8.Qe2 d5 9.Bxf6 Bxf6 10.Bb3 O-O 11.O-O a5 12.exd5 cxd5 13.Rd1 d4 14.c4 Qb6 15.Bc2 Bb7 16.Nd2 Rae8 17.Ne4 Bd8 18.c5 Qc6 19.f3 Be7 20.Rac1 f5 21.Qc4+ Kh8 22.Ba4 Qh6 23.Bxe8 fxe4 24.c6 exf3 25.Rc2 Qe3+ 26.Kh1 Bc8 27.Bd7 f2 28.Rf1 d3 29.Rc3 Bxd7 30.cxd7 e4 31.Qc8 Bd8 32.Qc4 Qe1 33.Rc1 d2 34.Qc5 Rg8 35.Rd1 e3 36.Qc3 Qxd1 37.Rxd1 e2 0-1
  </code></pre>
  
  <p>Edit: game 3 had an error in the PGN (2..Nc6 was 2..c6 instead)</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-01-21T10:45:50.260Z
Answers.LastActivityDate: 2020-01-25T09:58:58.887Z
Answers.LastEditDate: 2020-01-25T09:58:58.887Z
Answers.UserDisplayName: Remellion
Answers.Body: <p>While PhishMaster's answer is correct, we shouldn't forget about the importance of the <strong>d5</strong> square. If it wasn't for its weakness, Black would play <strong>...e5</strong> every single time in the Sicilian. By playing <strong>Nxc6</strong>, we are allowing Black to get rid of the main downside of his position, while also reinforcing his presence in the center.</p>
  
  <p>As pointed out by Akawall, <strong>5. Nb5</strong> forces  Black to play <strong>5...d6</strong>, in which case the Black-squared bishop cannot join the fight for the <strong>d5</strong> square (via <strong>b4</strong>) The only alternative would be to allow White to put a piece on <strong>d6</strong> which is not pleasant either</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-01-21T10:30:07.187Z
Answers.Text: A couple of notes: First, when black plays e5 in the Sicilian, the d5 square has been given the name the "Boleslavsky Hole" after Soviet GM Issac Boleslavsky. 100 years ago, such a move would have been considered a horrible positional blunder, but Boleslavsky showed us that black can work around a Nd5, and there were pluses to the position. So much so, that the related Sveshnikov Sicilian has become one of Magnus Carlsen's favorite weapons as black. https://en.wikipedia.org/wiki/Isaac_Boleslavsky#Boleslavsky_hole  Second, d6 is not force there at all, and leads to a line championed by
Answers.UserDisplayName: PhishMaster
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-01-21T10:34:13.720Z
Answers.Text: GM Ulf Andersson (at least on the ICC, if not OTB). 
  1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 e5 5. Nb5 a6 6. Nd6+ Bxd6 7. Qxd6 Qe7 (or Qf6). I used to watch him play this as a way often to lead to an endgame, his specialty.
Answers.UserDisplayName: PhishMaster
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-01-21T08:19:03.523Z
Answers.LastActivityDate: 2020-01-21T10:24:15.297Z
Answers.LastEditDate: 2020-01-21T10:24:15.297Z
Answers.UserDisplayName: David
Answers.Body: <p>First, it is important to know that in many Sicilian positions, not just the Kalashnikov, if black gets in d5, he has equalized, and has a very free game. Thus, taking on c6 helps black reinforce the center, and he will often get in d5 soon. White following up the trade with Bc4, which scores only 20% for white despite white out-rating black 2376 to 2192 per Mega 2020, makes it that much more impactful if black does get in d5 since white will be forced to lose yet another tempo.</p>
  
  <p>In addition, black will soon play Rb8 with a lot of pressure against b2, or if white plays b3, there will be chronic weaknesses on the queenside dark squares, and that could lead to Bb4xc3, and e4 may hang under certain circumstances. Black will also eventually get long-term pressure down both the b- and c-files, combines with a5-a4, should white exchange after an eventual d5 by black. These pawns may look strong, and they would be in the endgame, but in the middlegame, they are just huge targets on open files.</p>
  
  <p>Also, of note is that in most situations, if white plays the natural Bg5, either simply h6 wins the bishop pair, or Qa5 can get out of the pin tactically.</p>
  
  <pre><code> [FEN ""]
  
   1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 e5 5. Nxc6 bxc6 6. Bc4 (6. Nc3 Nf6 7. Bg5 $6 Rb8 8. Rb1 h6 9. Bxf6 (9. Bh4 $4 Qa5 10. Bxf6 Rxb2 $1 11. Kd2 Bb4 12. Rxb2 Bxc3+ 13. Kc1 Qa3 $19) (9. Bd2 d5 $17) 9... Qxf6 10. Bc4 Bc5 11. O-O O-O 12. Qe2 Bd4 13. Na4 d5 14. exd5 Bf5 15. dxc6 Qxc6 16. Nc3 Rfc8 {With huge pressure for the pawn.}) 6... Nf6 7. Nc3 Bb4 (7... Bc5 $5 {Is also possible, with the idea Bd4.}) 8. O-O O-O 9. Bg5 h6 10. Bh4 g5 11. Bg3 Qe7 12. Qd3 Rd8 13. Rfe1 d6 {And although white is holding it together, it is still not pleasant. The Bg3 is not doing much, the Qd3 is not comfortable being opposed by the Rd8, and black will continue trying to create weaknesses on the queenside with Rb8.}
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-01-20T16:15:42.977Z
Answers.LastActivityDate: 2020-01-20T16:15:42.977Z
Answers.UserDisplayName: PhishMaster
Body: <p>I get a lot of weaker players, who opt out of main lines, and they play 5.Nxc6?! against me. It has seemed to happen a lot lately. Why is that bad, and why shouldn’t white play that?</p>
  
  <p>Note: This is more of a teaching question as I intend to answer my own question.</p>
  
  <pre><code> [FEN ""]
  
   1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 e5 5. Nxc6?!
  </code></pre>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-01-20T16:21:32.353Z
Comments.Text: diagram or moves please
Comments.UserDisplayName: edwina oliver
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-01-23T11:59:10.420Z
Comments.Text: Hi, your post (by the way I found the discussions quite interesting) appears to have received a number of very decent answers already, including your own, please consider giving the post closure by accepting the answer that you find to be most fitting. Thanks for considering it.
Comments.UserDisplayName: user929304
Tags: <opening><sicilian-defense><kalashnikov>
Title: The Sicilian Defense Kalashnikov Variation: Why shouldn’t white play 5.Nxc6 here?
ThreadText: # The Sicilian Defense Kalashnikov Variation: Why shouldn’t white play 5.Nxc6 here?
  
  (Asked by: username_0 on 2020-01-20)
  
  I get a lot of weaker players, who opt out of main lines, and they play 5.Nxc6?! against me. It has seemed to happen a lot lately. Why is that bad, and why shouldn’t white play that?
  Note: This is more of a teaching question as I intend to answer my own question.
   [FEN ""]
  
   1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 e5 5. Nxc6?!
  
  **Tags:** opening, sicilian-defense, kalashnikov
  
  > **Comments:**
  > **username_1**: diagram or moves please  
  > **username_2**: Hi, your post (by the way I found the discussions quite interesting) appears to have received a number of very decent answers already, including your own, please consider giving the post closure by accepting the answer that you find to be most fitting. Thanks for considering it.  
  
  ---
  
  ## 3 answers
  
  ### Answer by username_0 on 2020-01-20. Score: 4 | Accepted answer
  
  First, it is important to know that in many Sicilian positions, not just the Kalashnikov, if black gets in d5, he has equalized, and has a very free game. Thus, taking on c6 helps black reinforce the center, and he will often get in d5 soon. White following up the trade with Bc4, which scores only 20% for white despite white out-rating black 2376 to 2192 per Mega 2020, makes it that much more impactful if black does get in d5 since white will be forced to lose yet another tempo.
  In addition, black will soon play Rb8 with a lot of pressure against b2, or if white plays b3, there will be chronic weaknesses on the queenside dark squares, and that could lead to Bb4xc3, and e4 may hang under certain circumstances. Black will also eventually get long-term pressure down both the b- and c-files, combines with a5-a4, should white exchange after an eventual d5 by black. These pawns may look strong, and they would be in the endgame, but in the middlegame, they are just huge targets on open files.
  Also, of note is that in most situations, if white plays the natural Bg5, either simply h6 wins the bishop pair, or Qa5 can get out of the pin tactically.
   [FEN ""]
  
   1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 e5 5. Nxc6 bxc6 6. Bc4 (6. Nc3 Nf6 7. Bg5 $6 Rb8 8. Rb1 h6 9. Bxf6 (9. Bh4 $4 Qa5 10. Bxf6 Rxb2 $1 11. Kd2 Bb4 12. Rxb2 Bxc3+ 13. Kc1 Qa3 $19) (9. Bd2 d5 $17) 9... Qxf6 10. Bc4 Bc5 11. O-O O-O 12. Qe2 Bd4 13. Na4 d5 14. exd5 Bf5 15. dxc6 Qxc6 16. Nc3 Rfc8 {With huge pressure for the pawn.}) 6... Nf6 7. Nc3 Bb4 (7... Bc5 $5 {Is also possible, with the idea Bd4.}) 8. O-O O-O 9. Bg5 h6 10. Bh4 g5 11. Bg3 Qe7 12. Qd3 Rd8 13. Rfe1 d6 {And although white is holding it together, it is still not pleasant. The Bg3 is not doing much, the Qd3 is not comfortable being opposed by the Rd8, and black will continue trying to create weaknesses on the queenside with Rb8.}
  
  
  ---
  
  ### Answer by username_3 on 2020-01-21. Score: 4
  
  This answer does not use modern analysis.
  One can always consult the old masters for advice.
  One of the first epic rivalries in chess was between an Irishman and a Frenchman: Alexander McDonnell and Louis Charles Mahé de la Bourdonnais. In the course of their six-match slugfest in 1834, this opening line arose thrice, with de la Bourdonnais taking 2 points out of 3 from the black side. What did he do?
  All three games went 1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 e5 5. Nxc6?! bxc6, a surprisingly modern opening.
  In this game, de la Bourdonnais' control of d5 and d6 was solid enough that he could forgo castling, play ...Ke7, and barrel down the kingside. Black had some attacking potential while white could not break through in the centre because the c6-pawn guarded d5 and b5; black's attack eventually petered out and he managed to hold a draw against white's slow queenside attack.
  [Event "London"]
  [Date "1834"]
  [Result "0-1"]
  [White "Alexander McDonnell"]
  [Black "Louis Charles Mahe De La Bourdonnais"]
  [FEN ""]
  
  1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 e5 5.Nxc6 bxc6 6.Bc4 Nf6 7.Bg5 Bc5 8.O-O h6 9.Bxf6 Qxf6 10.Nc3 a5 11.Kh1 d6 12.Qd2 g5 13.Rad1 Ke7 14.Na4 Bd4 15.Qd3 h5 16.Qb3 h4 17.f3 h3 18.g3 Bd7 19.c3 Rab8 20.Qc2 Ba7 21.Qd2 Rhg8 22.b3 Rbd8 23.Nb2 Rg7 24.Be2 Qg6 25.Nc4 Bc5 26.Nxa5 Rb8 27.b4 Bb6 28.Nc4 Qf6 29.Nxd6 Rgg8 30.Nxf7 Be6 31.Nd6 Rgd8 32.c4 Bxc4 33.Bxc4 Rxd6 34.Qxd6+ Qxd6 35.Rxd6 Kxd6 36.Rb1 Bd4 37.Bf1 Ra8 38.Bxh3 Rxa2 39.Bg2 Rb2 40.Rxb2 Bxb2 41.Bf1 Ke6 42.Kg2 Kf6 43.Kh3 Bc3 44.b5 cxb5 45.Bxb5 Bd4 46.Kg4 Be3 47.h4 gxh4 48.Kxh4 Bc5 49.Kg4 Bf2 50.f4 Bd4 51.Kf3 Bc3 52.Kg4 Bd4 53.Kh5 Bf2 54.Kg4 Bd4 55.Bd3 Be3 56.Kf3 Bd2 1/2-1/2
  
  The next example is a little different; early tactics saw mass exchanges down the e-file and yielded an entirely different sort of game, which again ended up drawn. Instead of 9...Nxe4 (which yields equality anyway), black could have tried other options to achieve the usual plan of ...d5 in the Sicilian. (Although in 1834, it was not "usual" in the slightest...)
  [Event "London"]
  [Date "1834"]
  [Result "0-1"]
  [White "Alexander McDonnell"]
  [Black "Louis Charles Mahe De La Bourdonnais"]
  [FEN ""]
  
  1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 e5 5.Nxc6 bxc6 6.Bc4 Nf6 7.Qe2 Be7 8.Nc3 O-O 9.Bg5 Nxe4 10.Bxe7 Nxc3 11.Qxe5 Re8 12.O-O Qxe7 13.Qxc3 d5 14.Bd3 Qd6 15.Rad1 Bd7 16.Qd4 c5 17.Qh4 g6 18.c3 Bc6 19.f4 c4 20.Bb1 Re2 21.Rf2 Rae8 22.f5 Qe5 23.Rdf1 Qe3 24.fxg6 fxg6 25.Qf6 Rxf2 26.Qxf2 Kg7 27.Qxe3 Rxe3 28.Kf2 Re5 29.Re1 Rxe1 30.Kxe1 1/2-1/2
  
  And for those who know the classics, this game is the one you've been waiting for since starting to read this answer. It is downright famous, and everyone should take a look. It is said that the problem with 5. Nxc6?! is in allowing black to strengthen the centre with more pawns -- and just look at the final position for the culmination of that strategy.
  [Event "London"]
  [Date "1834"]
  [Result "0-1"]
  [White "Alexander McDonnell"]
  [Black "Louis Charles Mahe De La Bourdonnais"]
  [FEN ""]
  
  1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 e5 5.Nxc6 bxc6 6.Bc4 Nf6 7.Bg5 Be7 8.Qe2 d5 9.Bxf6 Bxf6 10.Bb3 O-O 11.O-O a5 12.exd5 cxd5 13.Rd1 d4 14.c4 Qb6 15.Bc2 Bb7 16.Nd2 Rae8 17.Ne4 Bd8 18.c5 Qc6 19.f3 Be7 20.Rac1 f5 21.Qc4+ Kh8 22.Ba4 Qh6 23.Bxe8 fxe4 24.c6 exf3 25.Rc2 Qe3+ 26.Kh1 Bc8 27.Bd7 f2 28.Rf1 d3 29.Rc3 Bxd7 30.cxd7 e4 31.Qc8 Bd8 32.Qc4 Qe1 33.Rc1 d2 34.Qc5 Rg8 35.Rd1 e3 36.Qc3 Qxd1 37.Rxd1 e2 0-1
  
  Edit: game 3 had an error in the PGN (2..Nc6 was 2..c6 instead)
  
  
  ---
  
  ### Answer by username_4 on 2020-01-21. Score: 2
  
  While username_0's answer is correct, we shouldn't forget about the importance of the **d5** square. If it wasn't for its weakness, Black would play **...e5** every single time in the Sicilian. By playing **Nxc6**, we are allowing Black to get rid of the main downside of his position, while also reinforcing his presence in the center.
  
  As pointed out by Akawall, **5. Nb5** forces Black to play **5...d6**, in which case the Black-squared bishop cannot join the fight for the **d5** square (via **b4**) The only alternative would be to allow White to put a piece on **d6** which is not pleasant either
  
  > **Comments:**
  > **username_0**: A couple of notes: First, when black plays e5 in the Sicilian, the d5 square has been given the name the "Boleslavsky Hole" after Soviet GM Issac Boleslavsky. 100 years ago, such a move would have been considered a horrible positional blunder, but Boleslavsky showed us that black can work around a Nd5, and there were pluses to the position. So much so, that the related Sveshnikov Sicilian has become one of Magnus Carlsen's favorite weapons as black. https://en.wikipedia.org/wiki/Isaac_Boleslavsky#Boleslavsky_hole  Second, d6 is not force there at all, and leads to a line championed by  
  > **username_0**: GM Ulf Andersson (at least on the ICC, if not OTB).  1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 e5 5. Nb5 a6 6. Nd6+ Bxd6 7. Qxd6 Qe7 (or Qf6). I used to watch him play this as a way often to lead to an endgame, his specialty.  
  
  ---
  
  