Thursday, March 3, 2011

A chess960 special tactic?

Sometimes I do wonder whether out of all the possible tactical ideas in the opening phase that are possible in chess, they're not all seen in the standard chess SP518 opening. Could this be an example? I found it when I was playing on the other day (a great site for live Chess960). Notice that the opening phase is actually not yet complete arriving at move 14:

[Event "ChessCube Game"]
[Site ""]
[Variant "chess 960"]
[SetUp "1"]
[FEN "rkbnrbnq/pppppppp/8/8/8/8/PPPPPPPP/RKBNRBNQ w EAea - 0 1"]
1. e4 Nc6
2. Nc3 g6 
3. g3 d6 
4. f4 Nf6 
5. Bb5 Bd7 
6. d3 a6 
7. Bxc6 Bxc6 
8. Nd5 e6
9. Nxf6 Qxf6
10. Ne2 Bg7 
11. c3 Qe7 
12. Qf3 f5 
13. h3  fxe4 
14. dxe4 ...
Black to move: Find the standout winning move:

Ok here is where the real twist in the plot is. The hint is that the tactic is about the e4 square. But how does black break through? At the time I played d5?! which is not the answer. The answer is that here we see a tactic which is a kind of an x-ray tactic but not on a piece, but on a square (e4).
14. ... e5!      counter intuitively the only clearly best way to attack e4!
White is actually is in a kind of a zugswang! Lets assume that white decides to be very cautious and just keep developing some how and get his king out of the way of that terrible bishop fork attack of Bxe4+ (forking the queen and king)
15. Bd2 exf4 and black has opened up the e-file very quickly and the rest is fairly obvious:
16. O-O-O fxg3 17.Nd4 Bxe4 18. Qxg3 Qd7 - +
Ok so white decides that it is better to do something proactive. 
But this produces the ever present mating line!
15. f5... white wants to solve the problem of the light bishop forking attack 
16. Qxf5 Rf8      white has solved the problem but now white has an even bigger problem on the f-file!
17. Qxh7?? Bh6!! 18. Qxe7 Bxe4#

Fun eh! A duel bishop mate. A special tactic because of a unique Chess960 SP.

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