The Greek Gift Sacrifice
The greek gift is a classic sacrifice against a castled king. The key ingredients are (assuming white is offering the sacrifice) a knight on f3, a bishop on d3, and a Queen on d1. For the sacrifice to work white must have sufficient control of the g5 square for him to put his knight there without it being captured. It is usually necessary for white to be able to bring at least one more piece into the attack. The greek-gift is easiest to explain with an example. After the sequence 1. e4 e6, 2. d4 d5, 3. Nc3 Nf6, 4. e5 Nfd7, 5. f4 c5, 6. Nf3 Nc6, 7. dc Bxc5, 8. Bd3 O-O, (Diagram)
white can play the surprising (the first time you see it) 9. Bxh7+!. In this position, as in almost every greek gift type position there are five variations to calculate.
a) 9. ... Kh8. Well, this looks at first like black's safest option. He admits that he has made a mistake by castling and refuses to accept the sacrifice. White can try the move 10. Ng5 intending 11. Qh5 threatening 12. Bg6+ and 13. Qh7+ probably mate. Black my try to shuffle out to the way with 10. ... Re8, so that after 11. Qh5 and 12. Bg6 he can play 12. ... Kg8, 13. Qh7 Kf8, 14. Qh8+ Ke7, 15. Qxg7 Rf8, but black probably doesn't want to get involved with this. White has two pawns for nothing here and his attack continues.
b) 9. ... KxB, 10. Ng5+ Kh8?? This is terrible. White plays 11. Qh5+ Kg8, 12. Qh7 checkmate
c) 9. ... KxB, 10. Ng5+ Kg8? This is not much better. 11. Qh5 Re8, 12. Qxf7+ (simply to remove the f7 pawn) 12. ... Kh8, 13. Qh5+ Kg8, 14. Qh7+ Kf8, 15. Qh8+ Ke7, 16. Qxg7 checkmate
d) 9. ... KxB, 10. Ng5+ Kh6. This is the first of the tricky variations. Sometimes this move is not possible because there is no white pawn on f4 which means that white can win blacks queen with a discovered check from the bishop on c1 with the move Nxf7+ (or Nxe6+) if blacks queen is still on d8. Here then the move 11. f5 suggests itself. If 11. ... Qb6, then 12. Nxe6+ followed by 13. NxR restores the material balance. Alternatively white can play 12. Nxe6+ and reply to 12. ... Kh7, with 13. Qh5. Then after 13. ... Re8 (13. ... Rd8 loses to 14. Qxf7+ Kh8, 15. Qh5+ Kg8, 16. Qh7+ Kf8, 17. Qh8+ Ke7, 18. Qxg7 Ke8, 19. Qf7 checkmate) 14. Qxf7 Kh8, 15. QxR+ Nf8, (15. ... Bf8 loses to 16. Qh5+ Kg8, 17. Qh7 checkmate) 16. Qh5+ Kg8, 17. Qf7+ Kh8, 18. f6! wins. Throwing in Bf2+ at any point in this analysis doesn't help black at all (in fact it often loses even more quickly because it undefends the f8 square). I have not found an improvement over Qb6 which doesn't lead to immediate material loss. All this may sometimes be unnecessary however as white has the better 11. Qd3! (Diagram)
threatening 12. Qh7 checkmate as well as 12. Qh3+ Kg6, 13. Qh7 checkmate. Thus 11. ... g6 fails to 12. Qh3+ Kg7, 13. Qh7 checkmate and 11. ... f5 will also be met by 12. Qh3+ Kg6, 13. Qh7 checkmate, (11. ... Rh8, 12. Nxf7+ wins the black queen). I include the other lines because I am trying to present as many winning ideas as possible. Thus, if black had a knight on b4 and the d3 square were unavailable then the line with f5 would be the way for white to proceed.
e) 9. ... KxB, 10. Ng5+ Kg6. (Diagram)
Probably best. The position is very complex. I'm afraid I have to draw the line here, I can't give you a complete analysis. White may try Qd3+ or Qg4 or even f5+. Although I'm not going to present everything I will offer you a few ideas in the Qd3+ line. One is 11. Qd3+ f5, 12. ef e.p. Kxf6 13. Nh7+ 14. NxR which restores the material balance and allows whites attack to continue. 12. h4 is also worthy of consideration. For example, 12. ... Rh8, (12. ... Nb4, is better when after 13. h4 Kh6, white might try 14. Qg3!?) 13. h5+ RxR, 14. RxR KxR, 15. Qh3+ Kg6, 16. Qh7 checkmate.
Analysis by Alexander