Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...a6/4. Ba4/4...Nf6/5. O-O/5...Be7/6. Re1/6...b5/7. Bb3/7...d6/8. c3/8...O-O/9. h3/9...Bb7/10. d4/10...Re8/11. a4

=Ruy Lopez, Zaitsev Variation= On his sixth move Black weakened his queenside with 6...b5, and White's move is the typical probe to target this point. Black meanwhile plays ...h6 to prevent the forced draw with 12. Ng5 Rf8 13. Nf3, as the more consistent 11...Bf8 12. Ng5 Re7 is very awkward for Black. After these moves White usually continues with the consistent Nb1-d2-g3 maneuver to the kingside.

What follows is very deep strategy infused with sharp tactics. Some eighteen moves in, a pawn sacrifice becomes part of a major line. For example, after the moves 12...Bf8 13. Bc2 exd4 14. cxd4 Nb4 15. Bb1 c5 16. d5 Nd7 17. Ra3! (ready to bring the rook to the kingside when the time comes) f5! (countering with an attack in the center. This move attacks the base of White's e4-d5 chain, and it is shown that his center is unstable. Fortunately, he has more than enough resources, as shown in practice, in the form of an attack on the king) 18. g4! and the pawn sacrifice is here. White forfeits the center, but a malicious g4-g5 advance breaking open lines on the kingside is imminent. If 18...fxe4 19. Nxe4 Bxd5 20. g5 practice has shown that White wins much more often than Black because of his kingside pressure. Nevertheless, the position is difficult to handle, and often results in decisive games. For this reason the main line is 18...f4 19. Nb3 g5 20. Bd2 Bg7 21. Nbd4 when White is better simply because he has more space and Black's light squares are weak.

A seemingly more active move is 15...bxa4?!, which simply weakens the queenside pawns. White would do well to follow Kasparov—Karpov, World Championship 1990 and play 16. Rxa4 a5 17. Ra3 Ra6 18. Nh2! g6 19. f3!! The point: White relieves all pressure on his center and allows him to proceed with building up of an attack at his leisure. Black found himself struggling to find play of any sort, and quickly succumbed after a nice combination: 19...Qd7 20. Nc4 Qb5 21. Rc3 Bc8 22. Be3 c6 23. Qc1 Kh7 24. Ng4 Ng8 25. Bxh6! Sacrificing a piece temporarily to effect control over the dark squares in Black's camp. 25...Bxh6 26. Nxh6 Nxh6 27. Nxd6 Qb6! 28. Nxe8 Qxd4+? (Although it takes a pawn with check, the fact is that it opens up the d-file. Later analyses revealed that the immediate 28...Qd8! was superior, although Black's position is still difficult.) 29. Kh1 Qd8 30. Rd1 Qxd8 31. Qg5! penetrating onto the d-file. There then followed the inevitable marshalling of White's forces for a dramatic kingside attack: 31...Ra7 32. Rd8 Qe6 33. f4 Ba6 34. f5! Qe7 35. Qd2 Qe5 36. Qf2 Qe7 37. Qd4 Ng8 38. e5! Nd5!? 39. fxg6+ fxg6 40. Rxc6 Qxd8 41. Qxa7+ Nde7 42. Rxa6 Qd1+ 43. Qg1 Qd2 44. Qf1 and Black resigned.

Theory table
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'''1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7 6. Re1 b5 7. Bb3 d6 8. c3 O-O 9. h3 Bb7 10. d4 Re8 11. a4 h6 12. Nbd2'''

In this variation Black's queenside is weak and he lacks counterplay, as in Kasparov—Karpov, World Championship 1990.