Giving Up the Dragon Bishop for the Noble Steed
There are structures where black has a strong Bg7 on the open diagonal a1-h8. These positions can happen from Kings Indian, Dragon Sicilian, Benko etc. Usually white has his dark squared bishop on the c1-h6 diagonal, thus not opposing the bishop on g7. White has a Nc3 or Nd4 that block black’s bishop. Also in these structures white is the one who has more space in the centre: pawns on e4 and/or c4, while black has a pawn on c5 or no pawns in the centre at all. I would like to look at the exchange of this great bishop for one of white’s knights. This is a rather typical idea but if one does not know about it in advance it is rather hard to come up with it during the game. This is so because we give up a very strong piece (bishop) for seemingly less strong (knight) and this is something we don’t do by following our intuition. Giving up the Bg7 is a rather dangerous task- one should know for sure what advantages one will get in return. Black has to be careful not come under attack, since the Bg7 is a main defender of black’s kingside. I would like to list a few common compensations that black gets in return for exchanging the Bg7 for white’s knight.
1) Bad pawn structure that doesn’t let white bishops out, especially effective in the endgame.
In the pawn structure a2-b2-c4 when black takes the knight on c3 and white has to recapture with the pawn on b2 then white gets a destroyed pawn structure on the queenside. Black can start to attack the pawns on c3 and c4. Also, usually white's white-squared bishop white is in bad shape in such structures. This strategy is especially good when there are no queens on the board, since black does not have to worry about his weakened king position.
Lets look at one example. In the diagram below white has more space in the centre. Nd5 looks very strong if it were white to move. Black finds a way to create weaknesses for white at the expense of giving up the strong Bg7.
2) Undermine the e4 square and leave a bad Be2.
This is especially true if black takes knight on c3 not d4. Nc3 defends the e4 pawn, so by eliminating the knight black can either win the e4 pawn or take over the e4 square, which is a very important central square for both sides. If white has Bd3 then e4 is more reinforced than if the bishop is on e2. Lets take a look at an example of this strategy. In the following diagram white as usual has more space thus it is to black’s advantage to trade pieces, since any endgame is favorable for black due to their good pawn structure.
3) Closing up the position
Black gives away his black-squared bishop but has enough time to close the position with e5-f6. In closed positions knights are usually better than bishops. White would try to open the position to provide space for his bishops, while black would try to keep it closed. In the following position white has weak black squares on the queenside: b4 (after a4 advance), d4, while his dark squared bishop cannot cover them, since it is on h4. Black can opt for e:d5 and transferring to a Benoni type of structure but black finds another way to continue.
4) Simplifying the position
Sometimes the exchange on c3 can lead to massive piece exchanges that favor black. This is especially true if black is on the defensive and has less space. In such situations to ease the defense black would want to trade a couple of pieces. In the following position white is dominating. He has a simple plan of Rb1 and b4 when black has no counter play.
We looked at positions where black gives up his bishop for either Nd4 or Nc3. He has to be careful in doing so because the king on g8 becomes weak and if white can use it then black would be in trouble. If black can trade on c3 and destroy white’s pawn structure and get into the endgame he is in good shape. If black can take over the e4 square and use it to his advantage then trading for Nc3 would be justified. Giving up the bishop to close the position should be considered carefully since if white can break through eventually, black’s king would feel uncomfortable. At last, simplifications usually favor black if white has more space thus if black can enforce major piece trades he is doing well. Overall, one should know this technique and consider it during the game.
