The reason behind this is that while having the two bishops allows one to control greater swathes of the board, this advantage will be neutralized if the opponent's pieces are equally-- if not more-- active. Thus, their freedom should be limited to fully exploit the two bishops' capabilities.
Section 1: Restriction of enemy pieces
Take a look at the following position:
|Position 1: Black's pieces are shut in|
This is one of those dream positions that White would love to achieve! While there is no clear target for his bishop pair, he has been able to roll his front line forward to squeeze Black's minor pieces into a corner. The Black bishop is hemmed in by its own pawns, while the knight is being restricted by White's pawns and dark-squared bishop. This makes the activity of White's bishops even more significant, allowing them to support their advance of the pawns.
The restriction of enemy pieces is part of a strategical plan laid out by Wilhelm Steinitz:
- Suitable pawn advances to deny the enemy Knight (and Bishop) of vital operating bases
- Pressing the Knight (and Bishop) back into an unfavourable position
- Exploitation of the Knight (and Bishop)'s restricted power with an appropriate breakthrough at the right moment
An execution of this plan can be seen in Position 2:
Richter, Bernhard - Tarrasch, Siegbert
|Position 2: Position after White's 19th move|
In this game, Black has the two bishops and an open terrain. However, White's knight duo are powerful if not restrained; they can use outposts such as the c4 and e4 squares to interfere with enemy operations. Thus Black starts advancing his pawns to restrict the mobility of White's knights. The game continued:
19... c5 20. Ng3 h5 21. f3?!
While chasing the bishop away frees up the position for White's rooks, it also cuts off the knight on d2. Nimzowitsch suggested 21. a4 followed by 22. Nc4, fighting back by creating outposts for the knights.
21... Bd7 22. Re2 b5 23. Rae1 Bf8
The two bishops ensure that the rooks cannot breakthrough on the open file!
24. Nge4 Rg8 25. Nb3 Rc8 26. Ned2 Bd6 27. Ne4 Bf8 28. Ned2 f5
Taking away the e4 operational base from the knight.
29. Re5 Bd6 30. R5e2
Staying in Black's position with 30. Rd5 is met with 30... Rg6 followed by Bc6 trapping the rook.
30... Ra8 31. Na5 Rab8 32. Nab3 h4 33. Kh1 Rg6 34. Kg1 Be6
Black's bishops dominate the board, allowing his pawns to advance while forcing White's knights onto unfavourable squares.
35. Rf2 Ra8?
Giving White the chance to use a "subtle resource" (Nimzowitsch), which-- fortunately for Black-- Ricther fails to spot. Going straight for the breakthrough with 35... c4 would have been better according to Nimzowitsch.
Nimzowitsch: "A serious mistake. How could anyone allow ... a5 to be played without a fight? In answer to 36. Na5 Dr Tarrasch gives 36... Bc7 37. Nb7 Bf4 winning time for ... Rc8 and ... c4 by the threat of 38... Be3. He overlooks however, the hidden resource 38. Nxc5! Be3 39. c4 and Black cannot win, as the White Queenside is strong and the dark squares (c5 for the Knight) not less so."
36... a5 37. Nb1 a4 38. N3d2 (D)
|Position after 38. N3d2|
The hemming-in is accomplished. Now, the breakthrough occurs on the Queenside.
38... c4 39. Nf1
39. dxc4 is met with 39... bxc4 threatening c3, with the dark-squared bishop eyeing the a3 pawn.
39... Rc8 40. Kh1 c3 41. bxc3 dxc3 42. Ne3 b4
And White resigned a few moves later in light of the inevitable breakthrough. I will show the entire game here:
Section 2: Sample Games
The concept of the two bishops was the brainchild of Wilhelm Stenitz, father of positional play. Thus we shall pay tribute by studying how he puts his ideas to work. In the following games, you will witness a classical demonstration on how to restrict the enemy pieces using the bishop pair.
By exploiting his opponent's mistakes (9. f4 and 23. f5) Steinitz was able to hem in his opponent's pieces and fully utilize his bishop pair. In our next game, we will see how he is able to do the same thing even with minimal error from his opponent.
The games you have just seen are classics in the study of the double bishops. We can summarize the following:
- One way to maximize the two bishops' potential is to restrict the mobility of enemy pieces, be it putting your pawns on the same colour squares as the opposing bishop, or advancing them to hem in the knight.
- The two bishops control vital squares in the centre, suppressing the enemy and allowing friendly pieces and pawns to advance easily.
- Sometimes, trading off one of the bishops is necessary to neutralize an opponent's asset or obtain another advantage.
- To reiterate from Part 1, the bishop pair operates best in an open game.
In our final section, we will explore this topic in a different light: How to play against the bishop pair.
Part 1: http://nushsblackknights.blogspot.com/2015/05/foundations-of-two-bishops-part-1.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