Wednesday, May 13, 2015

Foundations of the Two Bishops (Part 1)

"The two bishops are a terrible weapon in the hands of a skillful fighter" -- Aaron Nimzowitsch

You might have heard of the bishop pair. We already know how powerful they can be in delivering a double-bishop checkmate. But as seen from Nimzowitsch's quote, they can only be effective if used properly. And that is what I want to talk about in this series of articles, so that in game-play you won't end up in this kind of situation:

Background image from Wiki

By the end of this series we should be able to understand how to execute the battle both with and against the bishop pair. With these in mind, we would be able to handle it confidently during a real game, and unleash its full potential to crush the opponent.


Section 1: Relative strengths of Bishop vs Knight

The strengths of the Bishop and the Knight differ according to the position. A Bishop is superior in open terrain, where the absence of pawns allow him to unleash his long-range powers. Compare this to a short-range Knight, which would have to hop several steps to reach a distant target. This is illustrated in Position 1:

Position 1: The White bishop is superior to the Black Knight

Here both sides have passed pawns, but White prevails because his bishop can stop the enemy pawn from the distance while Black's knight can't (you can work this out if you are not covinced)! Think about it like an first-person shooter: If you were trying to hit a target 300m away, would you rather spray from a distance with a machine-gun (Bishop) or run up to it with a grenade (Knight)?

On the other hand, the Bishop's long range powers become non-existent in closed positions, especially since he can only attack and defend squares of a certain colour. In such terrain, the short, hopping nature of the Knight prevails, for he can maneuver obstacles and attack any square he wishes. For visual explanation refer to Position 2:

Position 2: White's bishop is trapped

Here the bishop is weak; hemmed in by its own pawns, he cannot make inroads into the enemy position since there is no way he can magically hop onto the light squares!. On the other hand, Black's knight can still hop around and support pawn breaks like b4, or perform maneuvers like Nb6-Na5 to attack the opposing pawns. Back to our FPS analogy: In an urban environment where you are trying to take out an enemy behind a door, I'm sure throwing a grenade would be simpler than lugging a heavy machine-gun into the room. Unless you're Rambo.

Which if you were, you'd be outside breaking fences instead of reading this

So we see that the bishop's strength lies in its long range powers, while its weakness is its inability to cross obstacles and attack/defend squares of the opposite colour. Here I utilize a quote from Nimzowitsch's My System: "Now it suddenly becomes plausible why two Bishops are held to be so strong. The reason is clear, their strength appears doubled, the weakness which we underlined is neutralized by the presence of the "other" Bishop."

To visualize what Nimzowitsch described, look back to Position 2 and drop a White bishop on e2 and a Black bishop/knight on e7. Now White has better chances here, since his light-squared bishop can infiltrate the enemy position and clear the road for his pawns... and his dark-squared bishop.


Section 2: Attacking a pawn mass with a bishop pair

Take a look at the following impossible position (no kings):

Position 3: Lone bishop attacking a pawn mass

Here, White's lone bishop wants to attack a pawn mass. However, the weakness we described earlier becomes obvious: All Black has to do is to play 1... g6 and the light-squared bishop has no targets to attack!

Let's drop another White bishop on c2. Now-- as described by Nimzowitsch-- White's task becomes easier, since his bishops cover squares of both colour. Thus if Black were to push 1... g6, White would proceeds 2. Bb3 f5 3. Bg8 and Black's pawns will fall. Thus we see how the bishop pair works together; one bishop forces the pawns to move and clears the route for his partner to attack them. This phenomenon of two bishops side-by-side has a special name: The Horowitz Bishops. If used properly, they can have devastating effects against an enemy position.

Now let us look at the Horowitz Bishops in action against the enemy king:

Position 4: White to move

Here the White Queen works with the bishop pair to bombard the diagonals: 1. Qe4 threatening 2. h7#, forcing Black to respond with 1... g6. Now the long diagonal is opened for the dark-squared bishop to attack the enemy king: 2. Bd4+ winning the Queen.

Another example of the Horowitz Bishops can be seen after the moves 1. e4 e5 2. d4 exd4 3. c3 dxc3 4. Bc4 cxb2 5. Bxb2 Bb4+ 6. Nc3 Nf6 7. Nge2 Nxe4 8. O-O Nxc3 9. Nxc3 Bxc3 10. Bxc3 O-O? (D)

Position 5: Position after 10... O-O

With his 10th move Black has underestimated the ability of the two bishops to rake the kingside. 11. Qg4! g6 12. Qd4! and here mate on g7 cannot be stopped; the power of the bishop pair lies in the pin on f7.


Section 3: Other advantages of the Bishop Pair

Here I highlight another fundamental advantage that the two bishops bring. With greater control of the board, they are able to provide allied pieces and pawns with greater freedom of movement, and in turn restrict the motion of enemy forces by denying them of whole diagonals.

Michell, Reginald vs Tartakower, Saviely
Marienbad 1925
Position after Black's 39th move

In the above position, Black's two bishops dominate the kingside. This gives him an edge in the endgame, since his pieces and pawns will find it easier to advance down the board.


You can take note of how Black's bishop pair allowed his pawns, King and Rook greater freedom of movement down the board. In contrast, White's pieces and pawns were pushed to the edge due to Black's central dominance.


Section 4: Sample Game

I will finish off Part 1 with a sample game highlighting the power of the two bishops in an open position.

To summarize Part 1, here are the following points to take note:

  • A bishop pair is highly effective in attacking a pawn mass, since one bishop forces the pawns to move and opens the diagonal for his counterpart.
  • They also control critical diagonals in the centre, suppressing the opponent's pieces and allowing friendly pieces/pawns greater freedom to advance.
  • These advantages are best exploited in an open position, where the bishop is superior to the knight.

In Part 2, we will talk about other factors to consider when playing with the bishop pair.

Sources:
http://www.dailymail.co.uk/news/article-2129462/Italys-Cardinal-Rambo-defends-passion-guns.html
"The Bishop Pair" (Video Lecture) by IM Renier Castellanos, March 2015
"Modern Chess Strategy" by Ludek Pachman
"My System (21st Century Edition)" by Aaron Nimzowitsch

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