## domingo, 12 de novembro de 2017

### Xadrez - Mate em 53! (Sam Loyd)

 Samuel Loyd, American Chess Journal, 06/1879 (dedicado a Charles A. Gilberg).Código FEN: 8/5p1p/8/8/p3Q2K/rp5p/1p3ppr/b2N1bqk w - - 0 1.

As Brancas jogam e dão xeque-mate em 53 lances!

(White to play and give checkmate in 53 moves!)

PCFilho

#### 11 comentários:

1. 1. Qb1!!, and I have a plan: forcing the f1-Bishop to move, and delivering checkmate with Nxf2#.

To arrive in this situation, the White King will walk a long march, slowly forcing the Black pawns forward, until Black has no option but to move the Bishop and lose.

During the King march, Black will play the Rook from a2 to a3 to a2 and so on.

1. That is the correct key move. The plan is right, too.

The King march has to be careful, avoiding squares where it can be targeted by the Bishop.

With best play by both sides, the whole thing happens in 53 moves.

2. Actually, according to yacpdb.org it's mate in 50.

1. This problem was originally published as "mate in 75", and later corrected to "mate in 50". However, they missed a novelty in Black's 20th move, which delays checkmate in 3 moves. So it is indeed #53.

2. Are you going to post the full sequence? I'm curious about it. I think I have arrived in this move 20 you mention.

3. Yes, I'm going to write a detailed step-by-step solution, as usual. I will show both the 50-move and the 53-move sequences.

PS: 20. ... f5! is the move Black should play.

3. After the key 1. Qb1!!, Black cannot move his light-square Bishop, because of Nf2#.

White has to force this Bishop move, by "locking" all other Black pieces - being careful in the way, making sure the King cannot be attacked by the Bishop.

1. ... Ra2 2. Kg5 Ra3 3. Kf6 Ra2 4. Kg7 Ra3 5. Kg8 Ra2 6. Kf8 Ra3 7. Ke7 Ra2
8. Kd6 Ra3 9. Kc5 Ra2 10. Kb4 h6 11. Kc5 Ra3 12. Kd6 Ra2 13. Ke7 Ra3 14. Kf8 Ra2
15. Kg7 h5 16. Kf6 Ra3 17. Ke5 Ra2 18. Kd4 Ra3 19. Kc3 Ra2 20. Kb4!!

Now Black has to advance a Pawn. If he chooses to continue with 20. ... h4?, checkmate will happen in move 50:
21. Kc5 Ra3 22. Kb6 Ra2 23. Ka7 Ra3 24. Ka8 Ra2 25. Kb8 Ra3 26. Ka7 Ra2
27. Kb6 Ra3 28. Ka5 Ra2 29. Kb4 f6 30. Kc5 Ra3 31. Kd6 Ra2 32. Ke7 f5
33. Kd6 Ra3 34. Kc5 Ra2 35. Kb4 f4 36. Kc5 Ra3 37. Kd4 Ra2 38. Ke5 Ra3
39. Kxf4 Ra2 40. Ke5 Ra3 41. Kd6 Ra2 42. Kc7 Ra3 43. Kb8 Ra2 44. Ka8 Ra3
45. Ka7 Ra2 46. Kb6 Ra3 47. Ka5 Ra2 48. Kb4!!
48. ... a3 49. Kc5 Be2 50. Nxf2#
48. ... Ra3 49. Kxa3 Bd3 50. Nxf2#

However, Black can delay the checkmate in 3 moves, if he chooses to continue with 20. ... f5!. Then, checkmate will happen in move 53:
21. Ka5 Ra3 22. Kb6 Ra2 23. Ka7 Ra3 24. Ka8 Ra2 25. Kb8 Ra3 26. Ka7 Ra2
27. Kb6 Ra3 28. Ka5 Ra2 29. Kb4 h4 30. Ka5 Ra3 31. Kb6 Ra2 32. Ka7 Ra3
33. Ka8 Ra2 34. Kb8 Ra3 35. Ka7 Ra2 36. Kb6 Ra3 37. Ka5 Ra2 38. Kb4 f4
39. Kc5 Ra3 40. Kd4 Ra2 41. Ke5 Ra3 42. Kxf4 Ra2 43. Ke5 Ra3 44. Kd6 Ra2
45. Kc7 Ra3 46. Kb8 Ra2 47. Ka8 Ra3 48. Ka7 Ra2 49. Kb6 Ra3 50. Ka5 Ra2 51. Kb4!!
51. ... Ra3 52. Kxa3 Bd3 53. Nxf2#
51. ... a3 52. Kc5 Bd3 53. Nxf2#

4. This one is very similar in theme to the mate in 14 by Sam Loyd you posted a long time ago.

1. Yes, these problems are indeed very similar!

This is the problem you refer to:
Xadrez - Mate em 14! (Sam Loyd)

2. Yes, that's it!

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