E38 Nimzo-Indian: Classical, 4...c5 (1.d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.Qc2 c5 5.a3 cxd4)

I think this was the first time when not all of the opening moves were found in the LiveBook. The move 5...cxd4 had not been played at all. In my reference database the move 5...cxd4 had been played in 44 games and it had a score of 51.1%. The moves 5...Bxc3+ and 5...Qa5 were more often played and they were also more successful for the player controlling the black pieces. We followed previously played moves up to the move 7...O-O. Three games had reached that position and in two of them the move 8.e4 was played. One player had chosen to play 8.Bg5.

[Event "Live Chess"] [Site "Chess.com"] [Date "2016.07.19"] [Round "?"] [White "Kojjootti"] [Black "Vierjoki, Timo"] [Result "0-1"] [ECO "E38"] [WhiteElo "1712"] [BlackElo "1796"] [Annotator "Tactical Analysis 2.10 (30s)"] [PlyCount "64"] [EventDate "2016.??.??"] 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Qc2 c5 5. a3 cxd4 {E38 Nimzo-Indian: Classical, 4...c5} 6. axb4 dxc3 7. bxc3 O-O (7... b6 8. Bf4 Bb7 9. f3 Nc6 10. Bd6 Ne7 11. e4 Nc8 12. Bg3 Nh5 13. Bf2 e5 14. Ne2 h6 15. g4 Nf6 16. h4 Nd6 17. Ng3 Qc7 18. c5 Nc8 19. c4 d6 20. Qa4+ Kf8 21. cxd6 Nxd6 22. c5 {Ranasinghe,S (1721)-Buddhika,A (1183) Narahenpita 2017 1-0 (52)}) 8. Be3 $146 {-0.16/25} (8. e4 $14 {0.43/25} Nc6 (8... d5 9. e5 Nfd7 10. f4 dxc4 11. Bxc4 Nxe5 12. Be2 Ng6 13. Nf3 Qc7 14. g3 Nc6 15. Bd3 b6 16. Kf2 Bb7 17. Re1 Rac8 18. Re2 Rfd8 19. Ba3 b5 20. Be4 Qb6+ 21. Kg2 f5 22. Bxc6 Qxc6 23. Re3 {Zykiene,R (1912)-Sulikiene,K (1926) Kaunas 2015 1/2-1/2 (39)}) 9. Nf3 Qc7 10. Bg5 Ng4 11. c5 d6 12. cxd6 Qxd6 13. Be2 e5 14. h3 Nf6 15. Be3 b6 16. O-O Bb7 17. Nd2 Rfc8 18. Qb3 Nd8 19. f3 Ne6 20. Rfd1 Nh5 21. Nc4 Qc7 22. Bf2 Nhf4 23. Bf1 {Kuzmin,S (2249)-Egitov,A (2002) Novosibirsk 2007 1-0 (61)}) (8. Bg5 h6 9. Bh4 Nc6 10. Nf3 b6 11. e3 Bb7 12. Be2 Rc8 13. O-O a5 14. b5 Ne7 15. Rfd1 Ne4 16. Rd4 Nc5 17. Rad1 f6 18. Bd3 Rc7 19. Rg4 Qe8 20. Bg3 e5 21. Bh7+ Kh8 22. Nxe5 fxe5 {Schuffenhauer,R (1637) -Friedt,M (1766) Osnabrück 2011 1-0 (38)}) 8... a6 9. b5 {-0.47/24} (9. Bf4 $11 {0.13/26}) 9... a5 {-0.05/29} (9... b6 $15 {-0.47/24 feels stronger.}) 10. Nf3 $11 b6 11. Bd4 {-0.38/25} (11. c5 $11 {0.16/27}) 11... Bb7 12. Ng5 { -1.34/28} (12. c5 $1 $11 {-0.19/26 keeps the balance.}) 12... g6 {0.15/26} ( 12... Re8 $17 {-1.34/28} 13. Be5 h6) 13. Qd3 {-0.75/25} (13. h4 $11 {0.15/26} d6 14. h5) 13... h6 {0.00/26} (13... d6 $1 $17 {-0.75/25} 14. h4 Nh5) 14. Nf3 { -0.47/26} (14. h4 $11 {0.00/26 might be stronger.} hxg5 15. hxg5) 14... Re8 { 0.03/27} (14... d6 $15 {-0.47/26} 15. Be3 Qc7) 15. Qe3 Kh7 $2 {1.51/27} (15... d6 $1 $11 {0.00/26}) 16. h4 {0.49/26} (16. Qf4 $16 {1.51/27} Kg7 17. Qd6) 16... Ng4 {1.91/25} (16... d6 $14 {0.49/26}) 17. Qf4 {[#]} f5 {White should prevent . ..d6.} 18. Ne5 Nxe5 19. Qxe5 $40 {White wants a kill.} (19. Bxe5 $6 d6 $11) 19... Rg8 $2 {3.82/24} (19... Qe7 $16 {1.43/29}) 20. Qe3 $2 {0.62/26} (20. Qd6 $18 {3.82/24}) 20... a4 $2 {2.87/24 [#]} (20... Qe7 $1 $14 {0.62/26}) 21. Bxb6 Qc8 {3.14/22} (21... Qe8 {2.08/26 might work better.} 22. Bc7 d5) 22. Qd4 $2 { 0.90/26} (22. Qf4 $18 {3.14/22 is more deadly.}) 22... a3 $2 {3.29/23} (22... d5 $16 {0.90/26}) 23. f3 $2 {0.60/26} (23. Qd6 $18 {3.29/23}) 23... Re8 $2 { 3.92/27} ({Black should try} 23... d5 $1 $14 {0.60/26}) 24. e4 {aiming for h5.} e5 25. Qe3 fxe4 26. fxe4 Rf8 {3.00/23} (26... d6 {2.02/25 was necessary.} 27. Be2 Rf8) 27. g3 {1.54/25} (27. h5 $18 {3.00/23 hxg6+ would kill now.} g5 28. Bc5) 27... d6 $16 28. c5 {0.00/26} (28. h5 $16 {1.35/23 White wants to mate with hxg6+.} g5 29. Ba7) 28... dxc5 $2 {2.33/27} (28... Ra4 $1 $11 {0.00/26 and Black stays safe.} 29. c4 Nd7) 29. Bxc5 $18 Rf7 30. c4 ({But not} 30. Bxa3 $6 Ra4 $16) 30... Qg4 $2 {3.37/26} (30... a2 $16 {1.26/27}) 31. Be2 Qe6 $2 { 4.10/23} (31... Qxe4 {2.46/27} 32. Qxe4 Bxe4) 32. g4 $2 {0.16/27} ({Better is} 32. Rxa3 $18 {4.10/23} Nd7 33. Rf1) 32... a2 {1.41/25 Precision: White = 8%, Black = 12%. . Loss on Time!?} (32... Nd7 $11 {0.16/27} 33. Rxa3 (33. Bxa3 Rf4 $11) 33... Rf4 34. Rxa8 Bxa8) 0-1

These two games are the highest rated games that I was able to find that reached the position after 5...cxd4.

[Event "Bratto op 25th"] [Site "Bratto"] [Date "2005.08.24"] [Round "5"] [White "Buono, Michele"] [Black "Rombaldoni, Denis"] [Result "0-1"] [ECO "E38"] [WhiteElo "2133"] [BlackElo "2327"] [PlyCount "45"] [EventDate "2005.08.20"] [EventType "swiss"] [EventRounds "9"] [EventCountry "ITA"] [SourceTitle "CBM 108 ext"] [Source "ChessBase"] [SourceDate "2005.11.04"] 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Qc2 c5 5. a3 cxd4 6. axb4 dxc3 7. bxc3 h6 8. e4 d5 9. e5 Nfd7 10. f4 dxc4 11. Be3 Nc6 12. Qe4 f5 13. Qxc4 Nb6 14. Qb3 Qc7 15. Be2 O-O 16. Nf3 Nd5 17. Bc5 Nxf4 18. Bd6 Qb6 19. Bc5 Qc7 20. Bd6 Qd8 21. Bxf8 Kxf8 22. b5 Qb6 23. Qb4+ 0-1 [Event "Kecskemet 01-B"] [Site "Kecskemet"] [Date "2010.01.19"] [Round "5"] [White "Csala, Imre"] [Black "Peredy, Ferenc"] [Result "1-0"] [ECO "E38"] [WhiteElo "2168"] [BlackElo "2264"] [PlyCount "63"] [EventDate "2010.01.16"] [EventType "tourn"] [EventRounds "10"] [EventCountry "HUN"] [SourceTitle "CBM 134 Extra"] [Source "ChessBase"] [SourceDate "2010.03.03"] 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Qc2 c5 5. a3 cxd4 6. axb4 dxc3 7. Qxc3 d6 8. Nf3 O-O 9. Bg5 Nbd7 10. e3 b6 11. Bd3 h6 12. h4 Bb7 13. Nd2 Qe7 14. Rh3 Bxg2 15. Rg3 hxg5 16. hxg5 Nh5 17. Rxg2 g6 18. Qd4 a5 19. bxa5 Rxa5 20. Rxa5 bxa5 21. Ne4 Rb8 22. Nxd6 e5 23. Qd5 Kg7 24. Be2 Nb6 25. Qd3 Na4 26. Bxh5 Rd8 27. Nf5+ gxf5 28. Qxf5 Nxb2 29. Rh2 Rh8 30. Kf1 a4 31. Bxf7 Qxf7 32. Qxe5+ 1-0