## quinta-feira, 23 de novembro de 2017

### Xadrez - Mate em 2! (Robert Clyde Moore)

 Robert Clyde Moore, The Problemist, 2003.Código FEN: 5N2/2pQP2p/2PP1ppP/1P1kqbR1/1PN5/1P1P1K2/5B2/4R2B w - - 0 1.

As Brancas jogam e dão xeque-mate em 2 lances!

(White to play and give checkmate in 2 moves!)

PCFilho

#### 9 comentários:

1. Hint: the Black King, Queen and Bishop are in the same line as the White Rook.

This means that if the Queen moves, the Bishop will become pinned; and if the Bishop moves, the Queen will become pinned.

2. (In other words, Queen and Bishop are half-pinned.)

3. There is an astonishing number of "half-pins" in this problem!

4. That is exactly the goal of the author: he claims that this problem holds the world record of most half-pins in a chess problem. :)

5. How many half-pins are there in this problem?

6. According to the author, the solution explores 15 half-pins.

7. According to this source ( https://www.chessproblem.net/viewtopic.php?f=44&t=672 ):

"For over 80 years the world record for half-pins was 11. The man who finally broke the record, Robert Clyde Moore, worked on-and-off on the task for 30 years before he was successful. The new record of 15 half-pins was formerly thought to be impossible."

1. "Two units are said to be half-pinned [against the King] when one of them becomes completely pinned when the other moves." - this is how John Rice defines a half-pin in his "Chess Wizardry: The New ABC of Chess Problems".

In other words: when two chess pieces are half-pinned against the King, and one of them moves, the other becomes fully pinned – this is the "half-pin" theme in chess problems.

This problem currently holds the world record of half-pins, with 15 in total, all involving the Black Queen and Bishop.

1. Bc5!!
1. ... cxd6 2. Nb6#
1. ... fxg5 2. Rxe5#
1. ... Qxe7 2. dxe7# (1st half-pin: the Queen moved, and the Bishop became fully pinned, unable to stop checkmate by capturing the Queen)
1. ... Qxd6 2. Ke3# (2nd half-pin: the Queen moved, and the Bishop became fully pinned, unable to stop checkmate by interposing in the Bishop's attack)
1. ... Qe3+ 2. Kxe3# (3rd half-pin: the Queen moved, and the Bishop became fully pinned, unable to stop checkmate by interposing in the Bishop's attack)
1. ... Qe6/Qh2 2. Q(x)e6# (4th half-pin: the Queen moved, and the Bishop became fully pinned, unable to stop checkmate by capturing the Queen)
1. ... Qd4/Qc3/Qb2/Qa1/Qxe1 2. dxc7# (5th half-pin: the Queen moved, and the Bishop became fully pinned, unable to stop checkmate by capturing the Queen)
1. ... Qe4+ 2. dxe4# (6th half-pin: the Queen moved, and the Bishop became fully pinned, unable to stop checkmate by capturing the Pawn)
1. ... Qe2+ 2. Kxe2# (7th half-pin: the Queen moved, and the Bishop became fully pinned, unable to stop checkmate by interposing in the Bishop's attack)
1. ... Qf4+ 2. Kxf4# (8th half-pin: the Queen moved, and the Bishop became fully pinned, unable to stop checkmate by interposing in the Bishop's attack)
1. ... Qg3+ 2. Kxg3# (9th half-pin: the Queen moved, and the Bishop became fully pinned, unable to stop checkmate by interposing in the Bishop's attack)
1. ... Bxd7 2. Kf2# (10th half-pin: the Bishop moved, and the Queen became fully pinned, unable to stop checkmate by interposing in the Bishop's attack)
1. ... Be6 2. Qxe6# (11th half-pin: the Bishop moved, and the Queen became fully pinned, unable to stop checkmate by capturing the Queen)
1. ... Bg4+ 2. Kxg4# (12th half-pin: the Bishop moved, and the Queen became fully pinned, unable to stop checkmate by interposing in the Bishop's attack)
1. ... Bh3 2. Ne3# (13th half-pin: the Bishop moved, and the Queen became fully pinned, unable to stop checkmate by capturing the Knight)
1. ... Be4+ 2. dxe4# (14th half-pin: the Bishop moved, and the Queen became fully pinned, unable to stop checkmate by capturing the Pawn)
1. ... Bxd3 2. dxc7# (15th half-pin: the Bishop moved, and the Queen became fully pinned, unable to stop checkmate by interposing in the Queen's attack)

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