domingo, 17 de agosto de 2014

 Barry Jack da Costa Andrade, Chess World, novembro de 1949.Código FEN: 5nq1/1K1p3p/3N3b/1p3P2/1P3k1P/4N3/PB6/3BQ2n w - - 0 1.

As Brancas jogam e dão xeque-mate em 2 lances!
(White to play and give checkmate in 2 moves!)

*****

Um menino brincalhão retirou o Peão de "a2". Barry Jack pegou o Peão de volta, olhou atentamente o tabuleiro, colocou o Peão em "a3", e anunciou...
(A playful boy removed the Pawn from "a2". Barry Jack took the Pawn back, looked carefully at the board, put the Pawn on "a3", and announced...)

 Barry Jack da Costa Andrade, Chess World, novembro de 1949.Código FEN: 5nq1/1K1p3p/3N3b/1p3P2/1P3k1P/P3N3/1B6/3BQ2n w - - 0 1.

As Brancas jogam e dão xeque-mate em 2 lances!
(White to play and give checkmate in 2 moves!)

PCFilho

4 comentários:

1. One post, two problems.

Another pearl by Master Barry Jack!

3. I started by analyzing the set play for both diagrams, and I noticed that each position is a complete block. Every legal Black move leads to immediate checkmate:

1 ... Ne6/Qd5/Qg1/Qg3/Qg4/Qg5/Qg6/Qg7 2 N(x)d5#
1 ... Ng6/B moves/Q(x)a2/Qb3/Qc4/Qe6/Qf7/Qg2 2 N(x)g2#
1 ... Nh moves 2 Q(x)f2#

Therefore the task is to find a suitable waiting move. Obviously for each diagram the key move is different. But finding these keys is the challenge. For both diagrams, we eliminate the following units as candidates for the key thusly:

d6-knight: Moving it removes a guard from the f5-pawn, forcing the other one (the e3-knight) to stay put or else the king takes the pawn. All other checking moves also leave a flight square for the king.
e3-knight: Moving it allows ... Q(x)d5+.
b2-bishop: Moving it allows Black to retain both d5 and g2 with ... Qxa2.
d1-bishop: Moving it to the left unguards f3, moving it to f3 or g4 puts it en prise, moving it to e2 puts the e3-knight en prise, and moving it to h5 allows Black to block with ... Qg4.
f5-pawn: Moving it allows Black to retain both d5 and g2 with ... Qg5.
h4-pawn: Moving it unguards g5.
b4-pawn: It can't make a legal move.

So, it must be either the king or the a-pawn.

For the first diagram, it can't be the king, as Black can delay no matter where the king moves:

1 Ka6? 2 Qxa2+!
1 Ka7/Kb6? 2 Qg1! (pins the e3-knight)
1 Ka8/Kb8/Kc8? 2 Nf moves+!
1 Kc6/Kc7? 2 Qc4+!

Which leaves the a-pawn. Moving it to a4 allows Black to delay by capturing it. That means the key for the first diagram is 1 a3!!.

For the second diagram, the a-pawn is already on a3, so moving it is a no-no. Therefore the key is a king move. The only one that works is 1 Ka6!!, because the reason why that move didn't work in the first diagram doesn't exist here (with the pawn on a3, the a-file remains suitably closed).

4. Well done, Jake!! Absolutely perfect answer and explanation!! You are a chess-puzzle professor. :)

For the first diagram, 1. a3!! is the key move:
1. a3!!
1. ... Ne6/Qg7/Qg6/Qg5/Qg4/Qg3/Qg1/Qh8/Qd5+ 2. N(x)d5#
1. ... Ng6/Qg2+/Qf7/Qe6/Qc4/Qb3/Qa2/Bg5/Bg7 2. N(x)g2#
1. ... Ng3 2. Ng2/Qf2#
1. ... Nf2 2. Qxf2#

For the second diagram, 1. Ka6!! is the key move:
1. Ka6!!
1. ... Ne6/Qg7/Qg6/Qg5/Qg4/Qg3/Qg1/Qh8/Qd5 2. N(x)d5#
1. ... Ng6/Qg2/Qf7/Qe6/Qc4/Qb3/Qa2/Bg5/Bg7 2. N(x)g2#
1. ... Ng3 2. Ng2/Qf2#
1. ... Nf2 2. Qxf2#

I hope you have enjoyed this one! :)

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