Chess puzzle #1: Good bishop versus bad bishop
Chess puzzle #1: Good bishop versus bad bishop
I have often wondered how to proceed in endings or middlegames where one side has a bad bishop and the other has a good one. Here I offer a position that has a lot of interesting ideas:
So what ideas can you come up with? White has to play a few precise moves to begin with and he has to take into account all of Black's options. After having thought about the position, try to compare your ideas with the following analysis which is based on these six points:
- The opponent's tactics
- Our tactics
- Strategical analysis for both sides
- Candidate moves
- Concrete analysis
1) The opponent's tactics
It is White's turn to move but before looking at his options it's good to see what Black himself is threatening. The dynamic options can be boiled down to:
A) Checks: None.
B) Mate threats: None.
C) Captures: 1...Bxa4 is an option; it captures a pawn and gives Black a material advantage of one pawn.
D) Threats of captures: 1...b5 (threatening 2...bxa4) and 1...Bb5 (threatening 2...Bxd3). Both threats are obviously harmless since White can simply capture with his bishop: 2.Bxb5 and obtain a huge advantage.
Thus, Black's only real dynamic option is to capture the pawn on a4; 1...Bxa4. This should not be investigated immediately but just kept in mind (we first want a general overview of the position). Next we look at the dynamic options for White:
2) Our tactics
We make the same division of dynamic options for White:
A) Checks: None.
B) Mate threats: None.
C) Captures: 1.Bxg6 is an option; it captures a pawn and gives White a material advantage of one pawn. This seems to be an error because Black will have the option of recapturing with his f-pawn; 1...fxg6 and gain a material advantage of bishop for pawn. So it doesn't seem to work tactically.
D) Threats of captures: 1.b4 (threatening 2.bxa5); 1.Bb5 (threatening 2.Bxe8) and 1.Ba6 (threatening 2.Bxb7). These threats seem to be harmless because Black can himself capture White's b-pawn (1.b4 axb4) and can also capture White's Bishop (1.Bb5 Bxb5 or 1.Ba6 bxa6). One could try to make these threats work anyway by analyzing further but let's look at the situation from a more positional (or strategic) viewpoint first:
3) Strategical analysis for both sides
Ok, so now we know that there aren't any totally obvious ways to win the game by brute force (only 1...Bxa4 is an obvious threat to win a pawn). So the next step is to look at our options from a more long term perspective; namely to look at the strategic aspects:
In general, you have to be ahead by at least a rook to win without promoting a pawn if there is no immediate tactic available (with some exceptions). Thus, in this position White must promote a pawn or he cannot win. The question is how. Let's split our strategic thinking up into different areas:
A) Pawn play
B) Activating pieces
D) Prophylaxis/preventing the opponent's ideas
A) Pawn play: If we only look at pawns and ignore the remaining pieces then there is no way to create a passed pawn because the only white pawn that can move is the b-pawn and it cannot force its way through with 1.b4; either Black can 1) capture it with his a-pawn, 2) ignore it and just let White capture on a5 (since the two a-pawns can't get through anyway without the black b-pawn capturing the first pawn and blocking the second), or 3) he can reinforce the a-pawn by 1...b6, giving himself the option of taking on a5 (2.bxa5 bxa5), and afterwards there is no breakthrough for White. So there is no viable plan without the white bishop and/or king getting involved. This brings us to the next step.
B) Activating pieces: Let's compare the kings and bishops.
B1) The Kings: In the endgame, the kings generally want to be attacking either weak pawns, trapped pieces (including cutting off the opponent's king) or helping their own passed pawns by controlling the squares they need to go through in order to promote.
For the white king, the best square looks like b5, b6 and e7 because these squares both attack pawns that aren't guarded by other pawns while at the same time blocking the black king from threatening White's weak pawns. Thus, by getting the white king to one of these squares, you achieve more than one objective at the same time which is usually a good sign of the plan being sound.
For the black king, the targets are the a-, b-, d- and g-pawns. Thus, the squares b4, b3, c4, e4, f4, g4, h4 and h5 are his destination squares since from there he can attack the white weaknesses.
So what plan is there for either side to achieve their respective aims of activating the kings? Well, for Black it's mission impossible; there is no conceivable way to achieve his goals because White can block his path. However, for White the story is different. What is stopping White at the moment are the pawns on a5 and d5 (controlling b4 and c4, respectively); thus the plan should be to eliminate one of them; therefore the move 1.b4 suggests itself (removing the d5-pawn is not possible) followed by 2.Kb2, 3.Kb3 and 4.Kxb4 (assuming that Black played 1...axb4). We will analyze this in detail below but let's finish the strategic overview first.
B2) The bishops: The strength of the bishops depends to a great extent on the pawn structure; in this case the superior bishop is clearly the one on e3. It is a good bishop because the majority of the black pawns (and especially the centre pawns) are locked on light squares. This means that they can be attacked by the white bishop while the Black bishop can't attack any (except the a-pawn); therefore the black bishop is a bad bishop.
And there is also another aspect; the black bishop is also a passive bishop in the sense that it should normally not be behind its own pawns but in front. The same could be said of the white bishop but because the white pawns are so far advanced (White has a space advantage) it generally doesn't matter.
By the way, it is well-known that having a space advantage plus good bishop vs. bad bishop often means that you can make a sacrifice of your good bishop to create a breach in the opponent's structure. We will see this in a couple of variations below; namely the ideas of taking on g6/e6 (to create a passed f-pawn) and d5 (to enable the e-pawn to advance).
One last thing before moving on to exchanges. When the opponent has both a bad and passive bishop then you can often place him in zugzwang in various ways. For example after 1.Bb5 (threatening to take the black bishop), Black is very short of good moves.
C) Exchanges: The only pieces that can be exchanged are the bishops (the pawns have been examined under A). It should be crystal clear from the above that an exchange of bishops should benefit Black because his bishop is the inferior one by far. Thus, an exchange should only be considered by White if the resulting pawn ending is clearly winning; otherwise the bishops stay on board.
D) Prophylaxis/preventing the opponent's ideas: We will see this in the concrete variations that will commence below.
Ok, so what candidate moves and ideas do we have from the above? Here is a shortlist:
The ideas are formulated in words but have to be tested by variations; this will happen under the Concrete analysis below.
1) Activate the white king to b5/b6 in order to attack pawns and promote his own remaning queen-side pawn.
2) Use zugzwang against the black bishop since it only has one diagonal at the moment.
3) Sacrifice the bishop on g6/e6 in order to create a passed f-pawn or on d5 in order to let the e-pawn advance.
4) Block the position (from Black's point of view) in order to defend, i.e. prevent the white king from penetrating.
5) Win the a-pawn (Black's tactical threat at the initial position).
5) Candidate moves:
Based on all of the above, the following moves are worth considering for White:
A) 1.Bb5 - aiming to win a bishop by threatening it (and by zugzwang)
B) 1.Bxg6 - creating a passed f-pawn
C) 1.b3 - preventing Black's idea of capturing the a-pawn
D) 1.b4 - opening a route for the king to b5/b6
Only one of the above moves wins and it is 1.b4. But this is best proven by first seeing why the others fail.
6) Concrete analysis:
Let's look at option A:
1.Bb5 (threatening 2.Bxe8) 1...Bxb5 (Black's most forcing move should be examined first) 2.axb5 and we have the following position:
And now Black remembers his own defensive strategy and plays:
White can never break through the Black defensive setup; if he ever plays his pawn to b4, Black will either take it or just play a4 in order to prevent White from taking on a5.
Conclusion: The result is a clear positional draw, so 1.Bb5 is insufficient to win.
Let's look at option B:
1.Bxg6 fxg6 and we have the following position:
It should be clear that Black can simply stay behind with his king to prevent the passed pawn from advancing and still play his b-pawn to b6 if he just wants to defend. Maybe Black can even win but this is not interesting since we now know for sure that White has no chance to win.
Conclusion: The result is either a loss for White or an easy draw for Black, so 1.Bxg6 is insufficient to win.
Let's look at option C:
1.b3 (safeguarding the a-pawn) 1...Bd7 (giving the bishop more squares, not all on one diagonal and therefore eliminating any zugzwang ideas) 2.Kb2 (aiming for 3.Ka3 and then 4.b4) 2...b6 (protecting the a-pawn in anticipation of White's pawn thrust) 3.Ka3 Bc8 (just a waiting move) 4.b4 and we have the following position:
Black will of course never take on b4 since then the White king would gain access to this square. Instead he will just do nothing (his bishop is safe now) and if White ever pushes the b-pawn to b5 or there is an exchange on a5, then the position is still a positional draw since no one can make progress.
Conclusion: The result is a positional draw, so 1.b3 is insufficient to win.
Let's look at option D:
1.b4 (threatening 2.bxa5, opening a route for the king via b4 in order to attack the black b-pawn and win with his remaining queen-side pawn (or pawns depending on whether Black captures on a4); Black can't simply ignore the threat and lose material, his principal options are:
D1) 1...b6 (maintaining control of b4 to prevent the white king from penetrating)
D2) 1...Bxa4 (exchanging a-pawns but relinquishing control of b4)
D3) 1...axb4 (winning a pawn for the moment but relinquishing control of b4)
All of the above options lose but let's see why one option at a time.
D1) 1...b6 2.bxa5 bxa5 3.Ba5! and we have the following position:
Black can't capture because then White promotes, so:
3...Kf8 4.Kb2 ...
... and we have the zugzwang. Black has the option of either capturing on b5 or losing his bishop by moving either it or his king. Both options lose. Here are two sample variations to illustrate the main ideas:
1) Exchanging bishops:
4...Bxb5 5.axb5 Ke8 6.Kb3 Kd7 7.Ka4 Kc7 8.Kxa5 Kb7 9.b6 Kb8 10.Kb5 Kb7 11.Kc5 Kb8 12.Kd6 Kb7 13.Ke7 Kxb6 14.Kxf7 and White wins easily with his f-pawn.
The key idea in the pawn ending is to sacrifice the b-pawn in order to gain access to the e7-square from which the white king can attack the f7-pawn (like we looked at when examining the king's target squares).
2) Sacrificing the black bishop to maintain control of the b4-square:
4...Kg8 5.Bxe8 (this keeps b4 under control but...) Kf8 6.Bc6 (preparing to sacrifice on d5 when the white king reaches f4) Kg8 7.Kc2 Kf8 8.Kd2 Kg8 9.Ke3 Kf8 10.Kf4 Kg8 11.Bxd5! exd5 12.e6! fxe6 13.Ke5 Kf7 14.Kd6 and Black's pawns start to fall.
Conclusion: The result is a win for White, so Black's D1-option of playing 1...b6 loses.
D2) 1...Bxa4 2.bxa5 (this is losing mainly because Black has to defend both the b-pawn and preventing the sacrifice of the white bishop on g6) 2...Kf8 3.Kb2 Ke8 4.Ka3 Bd7 5.Kb4 Ke8 6.Kc5 Be8
(6...Kc7?! 7.Bxg6! - this is where the sacrifice comes in; it prevents the black king and bishop from untangling themselves)
7.Kd6! and Black is completely in zugzwang; in the next move White will play either 8.Ke7, 8.Bxg6 or capture the black b-pawn with his a-pawn. Black is lost.
Conclusion: The result is a win for White, so Black's D2-option of playing 1...Bxa4 loses.
D3) 1...axb4 2.Bc2
(2.a5 is a mistake because now Black can force an exchange of bishops and defend: 2...Ba4! 3.Bc2 Bxc2 4.Kxc2 Ke8 5.Kb3 Kd7 6.Kxb4 Kc6 and now there is no way to make progress because one would need to either win the b-pawn or reach e7 but neither objective can be achieved. White needs to have the idea of Bxg6 available in order to place Black in zugzwang)
2...Kf8 3.Kb2 Bd7 4.Kb3 Ke8 5.Kxb4 b6 6.a5 (soon Black will again be in zugzwang) 6...bxa5+ 7.Kxa5 Kd8 8.Kb6 Le8 9.Kc5 Kc7 10.Bd3 (White's threats of 11.Bxg6 and 11.Kd6 with zugzwang can only be prevented by 10...Kd7 but...) 10...Kd7 11.Bb5+ Kd8 12.Bxe8! Kxe8 13.Kc6! (this gains the diagonal opposition and wins the fight for the critical squares of the f7-pawn) 13...Kd8 14.Kd6 Ke8 15.Kc7 Kf8 16.Kd7 Kg8 17.Ke7 (reaching the e7-square again) 17...Kh7 18.Kxf7 and White again wins easily.
Conclusion: The result is a win for White, so Black's D3-option of playing 1...axb4 loses.
The overall conclusion is that White wins this interesting ending with 1.b4 and only this move. I hope that you've taken some ideas with you here, mainly these:
1. Normally don't trade a good bishop for a bad one
2. Good bishop + space advantage = sacrifices to create breaches
3. Bad bishop + passive bishop (in one) = zugzwang
I hope you enjoyed the above example! :)