[blind-chess] Spoiler Alert: Problem WAC119
- From: "Paul Benson" <paul.benson@xxxxxxxxxxxxxxx>
- To: <blind-chess@xxxxxxxxxxxxx>
- Date: Thu, 8 Jan 2015 03:43:44 -0000
Hello all,
This posting is divided into various parts. You can jump to the headings of the
sections by search/find for **, a pair of asterisks
.
** Positional evaluation of the problem
.
White: Two pawn islands with no weaknesses. The king is hiding in the corner
and as such is vulnerable to a potential back rank mate, there are 3 defensive
units nearby, the queen, the f1 rook and the d3 bishop, but how well are they
coordinating for defensive purposes? The a1 rook is 2 moves away from
centralisation to the d-file. The f1 rook is behind the advancing f-pawn, which
white might consider pushing as far as it can go, even thinking of sacrificing
it on the f6 square. The c1 bishop has limited options for development until
the blocking f4 pawn advances. The d3 bishop is pointing into the black
kingside but is temporarily blocked by the black e4 knight
.
Black: Three pawn islands. The doubled c-pawns will be weak in the ending. The
king on g8 is short of defensive piece cover, however the white pieces are a
few moves away from creating threats, so he is not in immediate danger. The
queen, despite being on her home square, is claiming some control down the
d-file. The e8 rook is ready for advancement down the e-file though there is a
blocking black knight in the way for the time being. The a8 rook can find some
activity down the b-file if thought useful. The bishop on c5 has control of
some important dark squares in the white centre / kingside. The knight on e4 is
excellently placed and combining harmoniously with the bishop to further
increase the control of those dark squares
.
** Proposed solution to WAC119
.
There are 2 weaknesses in the white position which black can exploit with just
1 plan. The 1st is the relative locations of the white king and queen, they are
in a potential knight fork formation. The 2nd is the white king being a
potential victim of a back rank mate. Black can easily and obviously execute
the 1st objective with, 1. ... Nf2+, a royal fork, which forces white to give
up an exchange with, 2. Rxf2 Bxf2, and black has a winning material advantage.
However, this does not expose the weakness of the white back rank. The key
players for black are the queen and e8 rook, and equally important are the
white non-contributing a1 rook and c1 bishop
.
Black plays, 1. ... Qxd3, removing the bishop which protects the f1 rook, an
undermining of an important defender. If white does not capture the black queen
then she will move away and black will simply have won a piece. So white must
play, 2. cxd3. Now black exposes the 2 weaknesses with, 2. ... Nf2+, that royal
fork, and white has 2 options. Firstly, to move the king with, 3. Kg1, but now,
3. ... Nxg4+, black wins the white queen and is a piece ahead, an easy win.
Instead the second option for white is after, 2. ... Nf2+, is to try, 3. Rxf2,
a deflection has occurred, and now the point of the black queen capturing the
white d3 bishop is revealed with, 3. ... Re1+, and after, 4. Rf1 Rxf1+ mate,
the weakness of the white back rank is proven. Had the white bishop still been
on d3, then the white rook could retreat to f1 and be protected
.
The black rook in the original position seemed fairly innocuous, and yet in
just 4 moves there was a back rank mate, beginning with the removal of a
defender of the f1 square, and immediately followed by a deflection of the only
defender of the back rank. Had the white c1 bishop not been on it's home square
then the white rooks would have been connected, and the black combination could
not work
.
** Condensed proposed solution
.
1. ... Qxd3 2. cxd3 Nf2+ 3. Rxf2 Re1+ 4. Rf1 Rxf1+ mate
.
** Other tactical variations considered, and rejected
.
Black can make a simple material gain with, 1. ... Nf2+, forking the white king
and queen. White must reply, 2. Rxf2, but after, 2. ... Bxf2, black has won an
exchange. This is good for black, and will give black a won game. It is however
not as efficient as the proposed solution of preparing the fork with the queen
sacrifice. If you selected, 1. ... Nf2+, you have not made a mistake, it is
just that the proposed solution is more clinical. If queens remain on the
board, white will have some threats for a while, though Black should be capable
of containing these. In the proposed solution white must choose between being
mated or being a piece down without queens in play, a much easier position for
black to convert to a win
.
** Alarm bells
.
1. Placing the king and queen in a potential knight fork formation comes with
dangers which should not be ignored
.
2. An x-ray attack can also apply to a potential invasion square
.
3. Connected rooks strengthen the back rank with regard to prevention of a back
rank mate. This formation does not guarantee safety, but will definitely assist
the defence
.
Paul Benson.
-----Original Message-----
From: Richard Dinger - Email Address: dmarc-noreply@xxxxxxxxxxxxx (Redacted
sender "rrdinger@xxxxxxxxxx" for DMARC)
Sent On: 12/12/2014 23:21
Sent To: chess - Email Address: blind-chess@xxxxxxxxxxxxx
Subject: [blind-chess] Problem WAC119
Problem WAC 119
Black to move
FEN:
r2qr1k1/
p1p2ppp/
2p5/
2b5/
4nPQ1/
3B4/
PPP3PP/
R1B2R1K
b - - 0 1
Short Algebraic Problem Setup:
White: Kh1, Qg4, Ra1, Rf1, Bc1, Bd3, Pa2, Pb2, Pc2, Pf4, Pg2, Ph2
Black: Kg8, Qd8, Ra8, Re8, Bc5, Ne4, Pa7, Pc6, Pc7, Pf7, Pg7, Ph7
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