411 REFERENCE · Wikibooks
Chess Opening Theory/1. d4/1...d5/2. c4/2...c6/3. Nf3/3...Nf6/4. Nc3/4...dxc4/5. a4/5...Bf5/6. Ne5/6...Nbd7/7. Nxc4/7...Qc7/8. g3/8...e5/9. dxe5/9...Nxe5/10. Bf4
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Carlsbad variation D17 Carlsbad variation
10. Bf4
This move pins the knight on e5 to the black queen, which is its only defender at the moment. Moving the knight isn't an option, so the only move to add another defender is 10...Nfd7.
10...Bd6?? fails to defend the knight because it loses a piece. The d6 square is attacked by both the c4 knight and the queen on d1 and only defended by Black's queen on c7.
Theory table
10... Nfd7 11. Bg2 g5 12. Ne4 gxf4 13. Nxf5 O-O-O 14. Qc2 10. ... ... 11. ... ... 12. Bxe5 Nxe5 13. Qd4 f6 14. O-O-O compensation 10. ... ... 11. ... f6 12. O-O Nc5 13. Ne3 Bg6 14. b4 +
References
See also