[blind-chess] Spoiler Alert Problem WAC087
- From: "Paul Benson" <paul.benson@xxxxxxxxxxxxxxx>
- To: <blind-chess@xxxxxxxxxxxxx>
- Date: Mon, 24 Oct 2011 22:11:17 +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, and an exchange down. The best white can hope for is
a draw, but this will require some poor play by black, rather than brilliancy
by white. There is a 4 against 3 pawn majority on the queenside/centre. This
mobile majority has the possibility of creating a passed pawn. Furthermore,
white is doubly attacking the undefended black c5 pawn from b4 and d4, though
it is doubtful if white can make gain by capturing with, bxc5, at some point,
since the a-pawn will become isolated and quickly lost. The d4 pawn is
defending the knight on e5, and so can not think of capturing the black c5
pawn. Both kingside pawns are isolated, they are not yet in danger of attack,
but should the position become open for the black rook, then white will be tied
down in some way to defending these pawns. The king is not in danger, and has
started the necessary advance into the centre of the board, to try to hold the
position. However, the king can not move too far from g3, since a potential
black, Rh6, will win the abandoned h3 pawn. The knight is placed on the best
possible square it could find for this position. It has an outpost, that is a
square on which it can not be attacked by an enemy pawn, from which it can
limit the activity of both the black king and rook. It blocks the only fully
open file, and so prevents the black rook from gaining entry into the white
position, a factor however, which effectively forces the knight to remain on
e5, unless there is a very good tactical reason to move elsewhere
.
Black: Three pawn islands, and an exchange ahead. The isolation of the a7 pawn
is not a problem in terms of being defended. However, should white play pawn
b5, then white will have a mobile pawn majority on the queenside, and this can
quickly create a passed pawn. The c5 pawn is doubly attacked and is not
defended at all. The d5 pawn is not in any danger, and at present is
contributing nothing to the game. The kingside pawns have a 3 against 2
majority, however because there are doubled pawns on the g-file, black will not
be able to create a passed pawn by force. The 4th rank pawns on f5 and g5,
sitting side by side, perform an effective barrier to the potential advance of
the white king. The king is in no danger, due to there only being a white
knight and pawns left. It must however, be careful as to which squares it
moves. The white knight has no immediate threats, but should the black king try
to advance, then potential knight forks are present, and some of these will
cost black a pawn. The rook is rather miserably placed. There are no fully open
files for it to occupy. It can only move sideways, and should it do so, it will
not find a target in the white position
.
** Hints section, 5 hints
.
Hint 1, to find the key move
.
It has been said that, "Fair exchange is no robbery", but just how fair is an
exchange here?
.
Hint 2, to find the key move
.
This one looks extremely fair from black's perspective, but what happens next?
.
Hint 3, to find the key move
.
Ah, now who is said to have a Colonel's baton in their knapsack?
.
Hint 4, to find the key move
.
In military terms, a little mobilisation is needed now
.
Final hint, to find the key move
.Oh yes, black still has a pawn undefended. However, sometimes, the best
defence is another attack
.
** Proposed solution to WAC087
.
A lengthy endgame seems to be in prospect for black here. That is a superficial
assessment. Tactics can immediately alter a position, and black has a
position-changing resource in the move, 1. ... Rxe5. This is returning the
exchange, in order to bring about a change in the dynamics of the pawn
formation. White has no choice but to recapture, so, 2. dxe5, and now it is up
to black to show what has changed in the position. The white pawn, previously
on d4 and now on e5, could be a tempting target for the black king. This is not
easy to assess at all, as will be shown later with a variety of sample lines,
rather than in depth analysis. No, the important change in the position for
black, is that a previously blocked centre, has now become dynamic. The d5 pawn
is now free to move with, 2. ... d4, and all of a sudden, white is about to
lose. Pay attention to the tension in the central pawn formation. White can
capture either of the black pawns, which in turn, means that black can also
capture either of the 2 white pawns. The most important feature of the mutual
confrontational formation, is in which direction the 2 pawn chains are
slanting. Black has a c5/d4 chain slanting into the centre. The white c3/b4
chain slants away from the centre. This means any white pawn capture will be
capturing into the centre. Alternately, any black pawn capture will be moving
away from the centre. So, why is this so important? It is all to do with the
distant location of the white king on the kingside, being too far away to
prevent one of the black pawns from promoting. There are 2 possible solutions
here, and they appear to be of equal merit, so neither shall be given the
status of being the main line
.
However, before getting to the solutions, there is a very important concept,
which frequently arises when calculating wether a passed pawn will promote, or
be caught by a retreating/approaching king. It is called "The Square". To
construct the square, one must imagine a smaller square, sitting within the 8
by 8 square of the chess board. From the viewpoint of the
retreating/approaching king, 1 corner of the square will be the passed pawn,
which is trying to promote. If the retreating/approaching king, can enter this
square on it's next move, then providing there are no hindering pawns, friendly
or enemy, and it's route to the passed pawn does not include squares controlled
by enemy pawns, then the king can catch the pawn
.
Here are 6 examples of how to imagine the square, all are given from the white
perspective, and all examples are relevant to the analysis.
Example 1: With a black pawn on b4, the square is from b4, down to b1, across
to e1, and up to e4, and back across to b4. Join up these four locations, to
construct a 4 by 4 square.
Example 2: With a black pawn on d4, the square is from d4, down to d1, across
to g1, and up to g4, and back across to d4. Join up these four locations, to
construct a 4 by 4 square.
Example 3: With a black pawn on c3, the square is from c3, down to c1, across
to e1, and up to e3, and back across to c3. Join up these four locations, to
construct a 3 by 3 square.
Example 4: With a white pawn on e5, the square is from e5, up to e8, across to
b8, and back to b5, and back across to e5. Join up these four locations, to
construct a 4 by 4 square.
Example 5: With a white pawn on b6, the square is from b6, up to b8, across to
d8, and back to d6, and back across to b6. Join up these four locations, to
construct a 3 by 3 square.
Example 6: With a white pawn on a6, the square is from a6, up to a8, across to
c8, and back to c6, and back across to a6. Join up these four locations, to
construct a 3 by 3 square.
.
So, to return to the solution, and a reminder of the moves so far: 1. ... Rxe5
2. dxe5 d4.
Solution 1: White plays, 3. cxd4, and black is given the choice of 2 captures,
One immediately wins, and the other loses. The capture away from the centre
with, 3. ... cxb4, wins for black. Note, the square is from the b-file, to the
e-file, and the white king is on g3, and can not enter the square on it's next
move. The pawn now on b4 will promote in 3 moves. This came about because, as
well as advancing a rank when making a capture, the nature of pawn captures
occurring diagonally, means the pawn has moved one file further away from the
white king.. Instead, if black decides the c5 pawn will capture to the centre
with, 3. ... cxd4, then the white king is now sitting in the square, the d-pawn
will not promote. Play could continue with, 4. b5, and white utilises the
outside pawn majority to create a passed pawn. The black king can not attempt
to run across to the b-file, since the white e5 pawn can then advance, leaving
the black king unable to stop both the passed white e-pawn, and a potential
white passed pawn further over on the queenside. So the black king tries to
remove the white e5 pawn with, 4. ... Ke6. White keeps advancing with, 5. a5,
and black captures, 5. ... Kxe5. White pushes on with, 6. b6, which threatens
to capture on a7, gaining both a rank and a file advantage on the pursuing
black king. So, black must play, 6. ... axb6, and now comes a lovely trick for
white. It is, 7. a6, passing the black b-pawn, and now the black king on e5 can
not enter the square, which starts on the c-file, so white promotes and wins.
Instead, The white capture with, 7. axb6, loses, as the black king can enter
the square with, 7. ... Kd6, and will catch the pawn. Play could go, 8. Kf3 Kc6
9. Ke2 Kxb6 10. Kd3 Kc5, and black is 2 pawns ahead, and winning
.
Solution 2: White tries to get the king into the queenside, to stop the black
pawns with, 2. Kf3. Black wins with, 3. ... dxc3, and the square of promotion
for the black c3 pawn starts on the e-file, so the white king must move again
with, 4. Ke3. Now black can calmly make another capture with, 4. cxb4. This
creates 2 connected advanced passed pawns, and the white king can never capture
both, since if he wanders to b3, and captures the black b4 pawn, then it steps
out of the square of promotion of the black c3 pawn, which moves to c2 and will
promote. Note, when the black pawn captured on c3, it gained both a rank and a
file, which forced the white king to keep moving across to re-enter the square
of promotion of the now c3 pawn, allowing black to win a 2nd pawn
.
Now for some lines where black starts off with the exchange of rook for knight,
but chooses not to push, 2. ... d4, as in the 2 proposed solutions just given.
Attempting to present the analysis with variations, and sub-variations
contained within, and sub-sub-variations contained further within, will produce
virtually indecipherable spaghetti. Instead, a series of sample variations,
where opening moves are repeated to a branch point may be easier to follow. All
analysis in the variations begins after the moves: 1. ... Rxe5 2. dxe5, and
here black must do something about the c5 pawn. The only serious move is, 2.
... cxb4, and white must play, 3. cxb4. Now it is black to play, and all
variations begin with black playing the third move of Ke6.
.
Variation 1: 3. ... Ke6, and white forces matters with, 4. f4. This protects
the e5 pawn, and now white is ready to create a queenside passed pawn, so black
must do something. If, 4. ... gxf4+ 5. Kxf4, again the e5 pawn is protected and
the queenside pawns are ready to roll. So, black can displace the white king
with, 5. ... g5+. White is forced to accept this with, 6. Kxg5, and black now
cuts off the white king from retreating with, 6. ... Kxe5. Black now has 2
passed pawns, while white has the passed h-pawn, and a threat to create a
queenside passed pawn. White can initiate a pawn race with, 7. h4 d4 8. h5 d3
9. h6 d2 10. h7 d1-Q 11. h8-Q+. Yes, white has promoted with check, and now
black has problems. If the black king steps onto the d-file, then 12. Qd8+,
wins the new black queen. So black should try, 11. ... Ke4 12. Qe8+, and black
must play, 12. ... Kf3. Note, if instead, 12. ... Kd3 13 Qd8+, forces a queen
trade, and then the white queenside pawns will force a quick promotion. So,
after 12. Qe8+ Kf3, and it looks as if black can struggle on for a while, does
it? No, white has the crushing, 13. Qh5+, skewering the black king and queen,
white wins
.
Variation 2: 3. ... Ke6 4. f4 gxf4+ 5. Kxf4 g5+ 6. Kxg5 Kxe5 7. h4, repeating
as above. Black varies with, 7. ... f4, and the race goes, 8. h5 f3 9. h6 f2
10. h7 f1-Q 11. h8-Q+. It is likely that black will soon lose the a7 pawn, but
the advancing black king will assist the advancement of the passed black
d-pawn. Chances seem favourable to white, but difficult for both sides to play
accurately
.
Variation 3: 3. ... Ke6 4. f4 gxf4+ 5. Kxf4, and now black tries to gain a
tempo on Variations 1 and 2 with, 5. ... d4. Now white prevents black from
deflecting the king from f4 with, 6. h4. Black must react quickly, and
eliminate the white e5 pawn, before white can create a queenside passed pawn.
So, it means, 6. ... d3, is necessary, to deflect the white king. Now, 7. Ke3
Kxe5, and now white must deflect the black king with, 8. b5 Kd5 9. a5 Kc5 10.
b6 axb6 11. axb6 Kxb6. So black has 3 pawns against 1, but is the white king
going to get at the black pawns? Play can continue with. 12. Kxd3 Kc5 13. Ke3
Kd5 14. Kf4 Ke6. If white plays passively, black will pick off the white h-pawn
and win. So, 15. Kg5 Ke5. Now, the white king can not stop the black passed
f-pawn from promoting, but surely white can get the h-pawn through? The game
could end with, 16. Kg6 f4 17. Kxg7 f3 18. h5 f2 19. h6 f1-Q 20. h7. So, what
can black do about the threatened h-pawn promotion? It goes, 20. ... Qf6+ 21.
Kg8 Ke6. What is this, black has just allowed, 22. h8-Q, and it must be a draw
now? No, the white king is in a mating net with, 22. ... Qf7+ mate. This
demonstrates that a passed pawn on a rook's file can be permitted to promote,
providing the defending king is close enough to the f7 or g6 squares to support
a check mate
.
Variation 4: 3. ... Ke6 4. f4 gxf4+ 5. Kxf4 d4, and now white instead tries to
create a diverting queenside passed pawn with, 6. b5. Again, black must
immediately eliminate the white e5 pawn, and then get queenside with the king
very quickly. So, the only way to kick the white king is, 6. ... g5+. Now the
white king can not capture the g5 pawn, because black simply pushes, d3, and
the square of promotion for this pawn is now along the black 6th rank, and the
white king can not retreat to catch it. Play continues with, 7. Kf3 Kxe5 8. a5
Kd5 9. b6 Kc6, the black king is catching the white pawns. Now, play continues
with,10. bxa7 Kb7 11. Ke2, heading to win the black d4 pawn. However, black has
a nice trick here with, 11. ... f4, the only move to keep the win. Play
continues with, 12. Kd3 f3, and the black f-pawn saves the d4 pawn, since
should the white king capture on d4, it will have advanced out of the square of
promotion of the black f3 pawn. Now, the white king can do nothing against the
2 black passed pawns, despite each of them being unprotected by another unit,
they are in fact protected by the threat of it's neighbour achieving promotion.
Play continues with, 13. Kd2 Kxa7 14. Ke1, and again, black must be precise
here to keep the win. Black recreates the pattern of 2 pawns on the same rank,
separated by one file, which guarantees safety for both of them or promotion
for one, if the other is captured. It goes, 14. ... d3, and the white king is
in zugzwang. If now, 15 Kf2, then, 15. ... d2, forces promotion, as the e2 and
e1 squares are in black's control. If instead, 15. Kd2, then, 15. ... f2, is a
mirror image, the squares e2 and e1 are still in black's control. A win for
black
.
Variation 5: 3. ... Ke6, and now white tries for immediate queenside activity
to divert the black king away from the centre with, 4. b5. Play continues, 4.
... Kxe5 5. a5 Kd6 6. b6 axb6 7 axb6. This is too slow for white, shown by, 7.
... Kc6 8. Kf3 Kxb6 9. Ke3 Kc5, and black is 2 safe pawns up, and wins
.
Variation 6: 3. ... Ke6 4. b5 Kxe5 5. a5 Kd6 6. b6 axb6, and white tries to
confuse matters by creating a passed pawn. So white plays, 7. a6, but black now
has passed pawns on b6 and d5. These are both isolated, but separated by just
one file, and will soon enter into a mutual protection scheme, as shown before.
However, firstly the black king must step into the square of promotion with, 7.
... Kc6. The white king begins his march with, 8. Kf3, this is far too slow, as
shown by, 8. ... b5 9. Ke3 Kb6 10. Kd4. The white king has stepped in front of
one of the isolated black pawns. The mutual protection scheme works for black,
by the unattacked pawn on the same rank simply advancing one square. If the
attacked pawn is taken, here it would be the d5 pawn, the white king would have
stepped outside of the square of promotion. So now black plays, 10. ... b4,
protecting the black d5 pawn with a threat of promotion. White can make no
progress, black will round up the white a6 pawn for a simple black win
.
Variation 7: 3. ... Ke6 4. Kf3, the white king decides to move to the centre,
before committing the queenside pawns to advancing. Play continues, 4. Kxe5 5.
Ke3, and now black must assess the position carefully. The 2 white queenside
pawns will always be a problem for the black king to solve. The king must
venture queenside at some point, and must be certain that black winns both the
white queenside pawns, without losing the black a-pawn. This will ensure a
black win, the white king will not have sufficient time to remove the central
black d-pawn and both the g-pawns, freeing the white h3 pawn to run up the
board, because the black a-pawn will queen several moves first. So, black needs
the king as close to the white queenside pawns, and also defend the d-pawn. It
must be, 5. ... d4+, vacating the d5 square for the black king. Play continues,
6. Kd3 Kd5, and now white is being squeezed. White can avoid commitment for
only 1 move with, 7. f3, which is met with, 7. ... g6, black does not move the
f5 pawn, this controls the e4 square. Now white must move a queenside pawn,
since a white king retreat allows the black king to invade on the c4 square,
and the white queenside pawns will fall. So, 8 b5. Note: if instead, 8. a5 a6,
blocks matters, and the white king must retreat and lose control of the vital
c4 square, black will win 2 pawns. So, now white has committed with, 9. b5,
which allows the black king to begin infiltrating with, 9. ... Kc5. Now white
has no way to defend the queenside pawns. Play continues with, 10. Kd2 Kb4 11.
Kd3 Kxa4 12. Kxd4 Kxb5. The outside passed black a7 pawn will force the white
king to remain on the queenside, while the black king wins all the white
kingside pawns, a black win
.
Conclusion of the 7 variations just given. In variations 1 and 2, black played
inaccurately,losing one, and struggling in another. It appears variations 3 and
4, which is white trying 4. f4 gxf4+ 5. Kxf4, has to be met with, 5. ... d4,
which will win for black. Variations 5 and 6, where white tries, 4. b5, also
win for black. Lastly, variation 7 shows how 4 Kf3 fails for white. Therefore,
from the initial diagram, the moves, 1. ... Rxe5 2. dxe5 cxb4 3. cxb4 Ke6,
produces a win for black, but finding these winning variations is very difficult
.
** Condensed proposed solution
.
Solution 1: 1. ... Rxe5 2. dxe5 d4 3. cxd4 cxb4
.
Solution 2: 1. ... Rxe5 2. dxe5 d4 3. Kf3 dxc3 4. Ke3 cxb4
.
** Other tactical variations considered, and rejected
.
There are doubtless many ways for black to win from this position, by firstly
resolving the problem of the attacked c5 pawn, and then slowly manoeuvring with
king and rook, along with carefully considered pawn moves. This would be a task
requiring reasonable technique, combined with continually having to avoid
making careless mistakes. Such mistakes arise due to a desire to end the game
quickly, patience in endgame play is a virtue. Playing in this manner, that is,
keeping the material advantage, can not be heavily criticised, since a win is a
win. However, a quick certain winning opportunity should be taken, if it is on
offer
.
Option A: It would be a serious positional mistake, though not a fatal one, for
black to close the queenside with, 1. ... c4. This makes the defence for white
much easier. The only way for the black rook to enter the game after that, will
be by trying to open the kingside. This should be possible of course, but will
need careful planning
.
Option B: Instead, black can open up the queenside a little with either, 1..
... cxb4, or, 1. ... cxd4, both captures will lead to white recapturing with,
2. cxb4, and, 2. cxd4, respectively. This now gives the black rook an
opportunity to invade down the fully open c-file. Black will first have to
retreat the king with, 2. ... Ke8, and follow up with the plan of, Re7, Rc7,
and infiltration with any of, Rc3, or, Rc2, or, Rc1, as thought appropriate.
Once the black rook has advanced into the white position, then the white
queenside pawns can be attacked from behind, and white will not be able to save
them all. When trying to attack pawns with a rook, attacking them from behind
is much more efficient, than trying for a frontal assault
.
** Alarm bells
.
1. Black was an exchange up, in a rook against knight ending, and should win
with careful play. Nevertheless, at each move giving up the material advantage,
to reach a won king and pawn ending must be constantly considered
.
2. When a pawn captures, it move sideways by 1 file, as well as forward by 1
rank. The initial rook capture, dragged the white d4 pawn to e5. This totally
altered the central pawn formation, from previously being blocked, to being
dynamic
.
3. Black met the attack to the undefended c5 pawn, by creating an attacking
confrontational, c5/d4 pawn chain, showing how to defend against an attack by
creating
an attack. This issued a challenge to the defensive white c3/b4 pawn chain.
The black d4 pawn was then attacking the undefended base of the white pawn
chain, usually a favourable attacking concept
.
4. The confrontational pawn chains slant in opposite directions. A pawn chain
which slants into the centre, will capture away from the centre. This was
crucial for black when playing pawn d4, taking advantage of the distance that
the white king was from the centre. Any capture by a black pawn in this
formation, simultaneously gains both a file further from the white king, and a
rank nearer to promotion
.
5. The Square. This concept, offers a quick method of calculating, as to wether
or not, a potential pawn promotion will succeed. Understanding this concept,
and being able to use it quickly, will save important time in positions where
pawn promotion is threatened
.
6. The black kingside pawn majority, due to having doubled pawns, could never
create a passed pawn by force. It is in king and pawn endings, when the
potential weakness of doubled pawns, becomes much more obvious
.
7. In the variations, where black chose to try to win the white e5 pawn with
the king, white was given a mobile outside pawn majority. As it happens, on
this occasion, white could not make any gain from this potential asset. This
was because the black king could win the e5 pawn, and still remain close enough
to prevent white queenside promotion
.
Paul Benson.
-----Original Message-----
From: R Dinger - Email Address: rrdinger@xxxxxxxxxx
Sent On: 14/10/2011 18:54
Sent To: chess - Email Address: blind-chess@xxxxxxxxxxxxx
Subject: [blind-chess] Problem WAC087
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 WAC087
Black to move
FEN Problem Setup:
8/
p3k1p1/
4r3/
2ppNpp1/
PP1P4/
2P3KP/
5P2/
8
b - - 0 1
Short Algebraic Problem Setup:
White: Kg3, Ne5, Pa4, Pb4, Pc3, Pd4, Pf2, Ph3
Black: Ke7, Re6, Pa7, Pc5, Pd5, Pf5, Pg5, Pg7
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07:39:00
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