[blind-chess] Spoiler Alert Problem WAC078
- From: "Paul Benson" <paul.benson@xxxxxxxxxxxxxxx>
- To: <blind-chess@xxxxxxxxxxxxx>
- Date: Mon, 1 Aug 2011 18:48:51 +0100
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: Three pawn islands. The b2 pawn is attacked by the black f6 bishop, but
the bishop is presently pinned to the black king. The split pawns on the
kingside are not weak in this position, but will need greater care in the
endgame, since neither can ever offer protection to the other. The king sits on
a semi-open g-file, but black can do little to exploit the slight exposure in
the kingside. The Queen is actively placed, pinning the f6 bishop to the black
king, but is also under attack from the black g6 pawn, which gives white a
problem. The white queen is the only defence to the f4 bishop, and she has no
safe move which keeps that piece protected. The 2 white rooks are ideally
centralised occupying the central files, the d1 rook is attacking the black
queen, and the e1 rook has an x-ray attack on the black e6 knight. The f4
bishop is active on the kingside, and also has a threat on the c7 pawn, should
the black queen move away. The knight on e4 is ready for action, either in the
centre, or on the kingside. All the white pieces are developed, and
contributing to the attack
.
Black: Two pawn islands. The queenside pawns are contributing nothing as of
yet. The kingside pawns are controlling a few squares over there, but there is
also a hole on g5, which could be a good location for a white minor piece,
though at the moment black seems to have defended this square with his own
minor pieces. The king is under pressure, and is also tied to defending the e6
knight.. There are 5 white attacking units, all centrally placed. To counter
this, black has only 2 minor pieces in front of the king, to offer protection.
The queen is both unmoved, and under attack from the white d1 rook, and it is
white to move. The a8 and h8 rooks are on their original squares, and
contribute nothing to the black position. The f6 bishop is pinned the king by
the white queen, and is thus paralysed The e6 knight looks a little vulnerable,
being protected by the king, and having an x-ray threat from the white e1 rook
hitting it
.
** Hints section, 5 hints
.
Hint 1, to find the key move
.
The white queen is attacked, so something must be done about that, right?
.
Hint 2, to find the key move
.
Positionally speaking, which looks the stronger piece, the black queen on d8,
or the white rook on d1? Aha, so do not sacrifice that one
.
Hint 3, to find the key move
.
This winning sequence is a powerful light-squared invasion, but which square
can it be on?
.
Hint 4, to find the key move
.
Perhaps Aim at a light-square weakness, and a different one may appear
.
Final hint, to find the key move
.
Check with the cavalry, to find out if this is the charge of the Light Brigade
.
** Proposed solution to WAC078
.
It might not be immediately obvious, but white has the opportunity for a
decisive light-square invasion. The black knight on e6 is only defended once,
and only attacked once. There is however, an x-ray attack on the black knight,
from the white e1 rook. If the white knight on e4 was suddenly removed from the
board, then white could solve the problem of the attacked queen on f5, by
simply capturing the e6 knight with check. Of course, pieces can not just be
removed like that, but there is still a means to achieve the end. White plays,
1. Ng5+, and the knight removes itself from the e-file with check, and places a
triple attack on the vulnerable black e6 knight. Black has no less than 6
replies to consider. Firstly, moving the king, will lose material as follows.
If, 1. ... Ke7, or, 1. ... Ke8, or 1. ... Kg8, white will reply to all 3 king
moves with, 2. Qxe6+. White has just won a piece, and more material, if not
checkmate in some lines, will soon follow. Secondly, if black tries, 1. ...
Kf8, or 1. ... Kg7, then white replies to both these king moves with, 2. Nxe6+.
Again, white has just won a piece, and this time with a royal fork. After any
black king move subsequent to this fork, white can just start the liquidation
process with, 3. Rxd8. So, 5 black king moves all lose. Ah, but after 1. Ng5+,
there are 6 replies for black. There is definitely a triple attack on the e6
knight, but surely, black can simply play, 1. ... Nxg5 which would stop the
check, while saving the black knight, and white still has the queen attacked.
Yes, these 3 factors are correct, so black just plays, 1. ... Nxg5, and white
must think again. So, what has changed?
.
Firstly, the e-file has now become fully open for the white e1 rook, but the
second feature, which makes this position winning for white, is what is perhaps
not so obvious. The black knight is now on g5, which means the white queen on
f5, is now supporting a rook invasion with check on the d7 square. So, 2. Rd7+,
and black has to lose the queen for a white rook, and there are 3 ways to do
it. Firstly, if 2. ... Kf8, then 3. Rxd8+ Rxd8 4. Qxf6+ Nf7 5. Re7, and black
is lost. Secondly, 2. ... Kg8 3. Rxd8+ Rxd8, note if black tries to save the
bishop with, 3. ... Bxd8, then 4. Qxg6+ Kf8 5. Re8+ is mate. So, after black
plays, 3. ... Rxd8, white achieves a material win with, 4. Qxf6, the black
bishop falls. The third reply, black can try, 2. ... Qxd7 3. Qxd7+ Kf8. Note
if, 3. Kg8, white wins a piece with, 4. Bxg5 Bxg5 5. Qd5+, forking the black
king and g5 bishop. So, white has a nominal 1 pawn plus, but can win further
material with, 4. Bxg5 Bxg5 5. Qxc7, with a few threats. The b7 pawn is
attacked, there is also, Qc5+, which will pick up the black bishop, and lastly
there is, Qe5+, which forks black's bishop and h8 rook. All of these threats
can not be parried, and it seems as if losing the b7 pawn is least ruinous, but
black will lose more material anyway, when the white queenside pawns get rolling
.
** Condensed proposed solution
.
1. Ng5+ Nxg5 2. Rd7+ Qxd7 3. Qxd7+ Kf8 4. Bxg5 Bxg5
5. Qxc7
.
** Other tactical variations considered, and rejected
.
Variation A: 1. Qxe6+
A good try for white, is to try and catch the black royalty in the centre,
hoping to pick up material along the way. With all 5 white pieces working,
there might be the startling, 1. Qxe6+. Well, that resolves the problem of the
attacked white queen, but just how much activity will follow, and remember, the
more active white pieces which are traded for inactive black pieces, is almost
certainly relieving the pressure on black. Here, black can not avoid capturing
the white queen, as any black king move allows, 2. Rxd8, and white has won a
queen and knight for a rook. So, 1. ... Kxe6, and now the white e4 knight has 7
legal moves, all unleashing a discovered attack on the black king. Remember,
any variation where white has to recover the black queen for the d1 rook,
leaves white an exchange down, and the attack will have dissipated, leaving
black safe. So, 2. Nc3+ Kf7, and black is safe. Or, 2. Nd2+ Kf7, and here white
can not even win black the black queen, the d-file is blocked, black is safe.
Or, 2. Ng3+ Kf7, black is safe. Or, 2. Ng5+, and this is preventing the
blacking from skulking away to f7, but he can go, 2. ... Kf5. The line could
continue, 3. Rxd8, leaving black with a 3-way choice of recaptures. Clearly,
the white knight on g5 would like the possibility of forking rooks on f7 if
allowed, so black's simplest reply is, 3. ... Rhxd8, and white is an exchange
down with no follow up, black is safe. Or, 2. Nc5+ Kf7, and black is safe. Or,
2. Nxf6+ Kxf6, and black is safe
.
So, now we arrive at white's 7th discovered check with the e4 knight, which is,
2. Nd6+, which neatly covers the f5 and f7 squares, but has similarly blocked
the d-file, down which the d1 rook was intending to win back the black queen at
some point. Black has 2 replies, the first is, 2. ... Be5. This move will
return some material, in order to give the black king the f6 square for flight.
The idea is after, 3. Rxe5+ Kf6, but now white has, 4. Ne4+ Kg7 5. Rxd8 Raxd8,
and white has 2 minor pieces for a rook, a technical win, but requiring
accurate technique in a long game. So, at last white has found a favourable
line, however, black does not have to give away the f6 bishop, there is a legal
king move in, 2. ... Kd7. Yet again, the white knight has 7 legal moves with
which discovered check will be given. Listing them all will reveal nothing, it
is hopefully apparent that if white is going to survive this, then a discovered
check must be found, which allows white to regain the black queen for the
knight, and not a rook, as in lines just given. There are 2 moves, either 3.
Nf7+ or 3. Nxb7+, and since white will be capturing the black queen on d8 with
the knight, the better move is, 3. Nxb7+, picking up a pawn on the way. So, now
the black king has 2 moves to the c-file, and paradoxically, the active choice
is the worse move. The reason for this, is the unprotected black bishop and
g-pawn on the 6th rank. So if, 3. ... Kc6 4. Nxd8+ Raxd8+, black is trying to
trade off an active white rook, and if now, 5. Rxd8, black must be careful. If
here, 5. ... Rxd8, then, 6. Re6+ wins the f6 bishop, So, black must play, 5.
... Bxd8, but the same idea again for white, 6. Re6+ Kc5 7. Rxg6 Kxc4. It might
seem as if black is grovelling out, but here is a sting in the tail, white has,
8. Bxc7, which leaves white 2 clear pawns up, since, 8. ... Bxc7 9. Rc6+,
regains the bishop and wins. So, now back to the second king move which from
the start is, 1. Nxe6 Kxe6 2. Nd6+ Kd7 3. Nxb7+ Kc8, and now the king is not
vulnerable to a 6th rank check. so now, 4. Nxd8, and black must choose
carefully here. The better reply is 4. ... Bxd8, since capturing with the rook
by black, would allow a trade of rooks, and the remaining white rook will
invade firstly onto the 6th rank, win the g6 pawn, and have a deadly threat of
a check on the 8th rank, skewering the king and a8 rook, so black must take
time to avoid this. White can then safeguard the queenside pawns with, b3, and
then return to win the weak black h-pawn. So, after, 5. ... Bxd8 6. Re6 Rg8,
and white is a pawn up, better placed, but there is still much work to do
.
These lines with white, 1. Qxe6 demonstrate some possibilities for a pair of
rooks on fully open central files, combined with a couple of minor pieces,
against an undeveloped black army. It might also demonstrate, a centralised
knight, with numerous potential discovered checks, needs careful tactical
calculation skills
.
Variation B: 1. Qxf6+
White can achieve a slight material gain, and also set a little trap with, 1.
Qxf6+. Clearly, black has only one reply, 1. ... Qf6, and white now has 2
choices. The first, is to keep trading with, 2. Nxf6, hoping for a blunder,
since, 2. ... Kxf6, loses an exchange to, 3. Be5+. Black will not comply, and
simply play, 2. ... Nxf4. White has the better piece development, but no more,
this looks equal. Instead of capturing the black queen, white has an
interesting idea in, 2. Rd7+, setting a trap. If black tries for material
equality, white will soon crush black. For example, 2. Kf8, intending to let
the queen go, and regaining material equality by capturing the white f4 bishop.
Note, black should avoid, 2. ... Ke8, which loses to, 3. Nxf6+ Kf8 4. Rxe6. So,
now white takes the black queen with, 3. Nxf6, and black takes the white bishop
with, 3. ... Nxf4. Material is equal, but the position becomes crushing for
white with, 4. Ree7. Doubled rooks on the 7th rank, combined with a 6th rank
knight, set up a neat mating net. Black can try, 4. ... Nh3+ 5. Kf1 Ng5, which
stops the threatened mate on f7. However, white attacks the defending black
knight with, 6. h4, and any move by the black knight, allows 7. Rf7+ mate.
Black can only avoid mate with, 6. ... Rh7, but simply, 7. Nxh7+ Nxh7 8. Rxh7
white, a whole rook up, wins
.
So, after white's tricky, 2. Rd7+, black being a piece up, offers the queen
back with, 2. ... Qe7. White can play simply with, 3. Rxe7+ Kxe7 4. Ng5, and
the black e6 knight is pinned and lost, and white is better, but a long game is
in prospect. Instead, after black interposes with, 2. ... Qe7, white can create
complications with, 3. Ng5+. Black has 3 replies. Firstly, 3. ... Nxg5, which
loses to, 4. Rexe7+ Kf6, protecting the g5 knight, but then, 5. Be5+ wins an
exchange on h8. Secondly, 3. ... Ke8 4. Rxe7+ Kxe7 5. Rxe6+, and white also
wins the g6 pawn, and with two minor pieces and a passed f-pawn against a rook,
white will eventually win, but will need patient technique. The third black
choice after, 3. Ng5+, is, 3. ... Kf6. This is very bold, sometimes moves like
this will save the position, and sometimes they just march the monarch to his
doom. White continues with, 4. Rxe7, and if black plays, 4. ... Kxe7, this
transposes to a line just given, where the black knight and g6 pawn fall.
Instead, black can try to make use of the advancing king with, 4. ... Nxf4.
Material equality is again temporarily reached, but the position has imbalance.
White can try 5. Nh7+, forcing the black king up the board, hoping for a mate.
After, 5. ... Kf5, white does not have enough to mate the black king, the
square h4 is a haven, should white try to force matters. White can instead grab
a pawn with, 6. Rxc7, which leaves black to protect the b7 pawn, however, the
black f4 knight covers the g2 square, so if the white e1 rook ever moves off
the back rank, then the white king is vulnerable to a potential back rank mate.
White is better, but must be careful
.
Variiation C: 1. Rxd8+
There is a phrase in chess which says, "Obvious, therefore dubious", I think by
Bobby Fischer. This is clearly a generalisation, meant to make one think about
every move carefully, and not to be lazy, in the move-decision department.
Captures and recaptures, no matter how tempting, should not be automatic. Here,
with the black queen attacked, it is tempting to just take her. This would be a
mistake, both on tactical and positional grounds. Firstly, the black queen is
not active, and the white queen is very actively placed, with good attacking
opportunities. So, selecting a line which effectively trades queens is almost
always certainly a poor decision. Also, more active white pieces will be traded
for inactive black pieces. White will be slightly worse after, 1. Rxd8 gxf5 2.
Rxa8 Rxa8, and now white has both minor pieces attacked. The only move to avoid
material loss is, 3. Nxf6, and black can choose to capture either the f6
knight, or the f4 bishop. The simpler move is, 3. ... Nxf4, leaving white to
find a move for the f6 knight. Black has a slight gain in space, white must
play carefully. The white position has lost all momentum by entering a line
which trades 3 pairs of actively placed units
.
Variation D: 1. Nd6+
White already has an x-ray attack on the black e6 knight, from the e1 rook, and
now tries to be able to safely capture on e6 with the attacked queen. So, white
clears the way with, 1. Nd6+, and now black has 3 replies. Attempting to run
away with, 1. ... Kg7, looks awful. Simply, 2. Qxe6, and now black must take
the knight on d6 with, 2. ... Cxd6, but now the white heavy pieces run rampant
with, 3. Rxd6, forcing the black queen to keep a defence on the f6 bishop with,
3. Qf8. However, 4. Rd7+, and the black king cannot move, note that the white
f4 bishop covers h6, and now black loses bishop and queen for a white rrook
with, 4. ... Be7 5. Rxe7+ Qxe7 6. Qxe7+. So with, 1. Nd6+, black can try, 1.
... cxd6, which transposes directly into the line just given after, 2. Qxe6
Kg7. Note, if the black king goes, 2. ... Kf8, then, 3. Rxd6, and the black
queen is attacked by the rook, and the f6 bishop is doubly attacked by the 6th
rank force of white queen and rook. The queen must move, and the f6 bishop is
lost next move
.
So, thus far, 1. Nd6+ seems very promising. However, black has a shocking third
reply in, 1. ... Qxd6. Now matters are complex. White can capture the black
queen in 2 ways, but the white queen is also attacked. The supposedly weak
black knight on e6, is now doubly attacked, but also doubly defended. There is
also the white f4 bishop, which is defended once, but under a double attack
from the black queen and knight. What this means, is that white, now a piece
down, must find a reply which solves the problem of his attacked bishop and
queen, and also regain material. If white tries, 2. Qe4, black can avoid the
unnecessary complication of, 2. ... Qxf4, which should win, but simply play, 2.
Qc6, challenging the white queen and removing herself from the white rook's
threat. Black will then consolidate, and be winning. There is also, 2. ... Qe7,
which seems to leave black a piece ahead, but the central white rooks and queen
are still powerfully placed, and the black queen is hiding behind a potentially
vulnerable e6 knight. Careful play by black will slowly unravel the position,
but why should black permit such pressure, when, 2. Qc6, is a good and safer
challenge. So, What has white against, 1. ... Qxd6. It seems the only chance
is, 2. Rxd6, and black has no choice but to regain material with, 2. ... gxf5.
Now the point of white capturing the black queen on d6 is revealed, the black
e6 knight is doubly attacked by the white rooks, so, 3. Rdxe6, and material
equality is re-established, though black must be more careful here, the c7 pawn
is attacked, and the f6 bishop is presently tied down to prevent a white rook
invasion on the e7 square. After, 3. ... c6, black can then start challenging
the white rooks control of the e-file, and it seems black is equal
.
** Alarm bells
.
1. Black has fallen seriously behind in development. Only 2 minor pieces
developed, against 5 active white units. Hoping to survive against these odds,
is rather too optimistic
.
2. Both queens were under attack at the start. White forced matters in such a
way, that the black queen fell, while the white queen was under attack all the
time. This takes nerve, and confidence in one's ability to calculate
.
3. When so far ahead in development, it can be very tempting to analyse all
sort of fanciful variations. The original position, offers much food for
tactical thought. Be aware, that fantastic combinations are uncommon, and
winning attempts like, 1. Qxe6+, analysed in "rejected moves, variation B",
will be rare
.
Paul Benson.
-----Original Message-----
From: R Dinger - Email Address: rrdinger@xxxxxxxxxx
Sent On: 26/07/2011 20:17
Sent To: chess - Email Address: blind-chess@xxxxxxxxxxxxx
Subject: [blind-chess] Problem WAC078
Good Morning Puzzlers,
This problem is from Mario Lang's puzzle web page at
http://delysid.org/chess/epd.cgi
and is reported to be from Fred Reinfield's book "Win At Chess" 1958.
Problem WAC078
White to move
FEN Problem Setup:
r2q3r/
ppp2k2/
4nbp1/
5Q1p/
2P1NB2/
8/
PP3P1P/
3RR1K1
w - - 0 1
Short Algebraic Problem Setup:
White: Kg1, Qf5, Rd1, Re1, Bf4, Ne4, Pa2, Pb2, Pc4, Pf2, Ph2
Black: Kf7, Qd8, Ra8, Rh8, Bf6, Ne6, Pa7, Pb7, Pc7, Pg6, Ph5
No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 9.0.901 / Virus Database: 271.1.1/3789 - Release Date: 07/26/11
07:35:00
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