OCBs in the endgame(1)
Black is a pawn down. Should he keep pieces on and try to get counterplay, or bring about exchanges?
1...Nxc3! 2.Bxc3 [2.bxc3 would be better; White has better chances of using his extra pawn if he keeps rooks on.] 2...Rxd2! 3.Bxd2 Kg8
In an opposite-coloured bishops ending, one pawn up is normally not enough to win, unless there are other advantages. Here Black can draw easily.
4.Bc3 f6 5.f3 Kf7 6.Kf2 Ke6 7.Ke3 Kd5 8.Bb4 g6 9.Bf8 h5 10.Be7 f5 11.Bd8 Bb5 12.h4 Bf1 13.g3 Bb5 14.b3 Ke5 15.Bc7+ Kd5 16.Kf4 Ke6 17.Kg5 Kf7 18.a4 Bc6 19.Kf4 Ke6 It has become clear that White cannot make progress.
With a two pawn advantage in an opposite bishops ending, the winning chances are much better.
When the two extra pawns are connected, the main points to remember are:
a) to have any chance of a draw the weaker side's king must be in front of the pawns;
b) the pawns usually win if they can reach the sixth rank; with the pawns further back, the weaker side has good chances of a draw.
1.Bb5 Bf6 2.Ke4 The plan is simple; get the king to f7 and push the e-pawn. 2...Bg5 3.Kf5 Bh4 4.Kg6 Black is in zugzwang; the white king does not even have to get to f7 now. 4...Kc8 5.e7 +-
To draw, Black must prevent the pawns from reaching the 6th. The only way is to prepare to give up his bishop for both pawns by Bg4 or Bf7; does it make any difference which Black chooses? 1...Bf7! is a simple draw. The e-pawn cannot advance to e6 without the support of the white king, but the king cannot leave the defence of the d5 pawn, so White can make no progress. All Black has to do is shuffle his bishop between f7 and g8.
[Note that 1...Bg4? is weaker, since White can manoeuvre with his king and achieve the advance e6, e.g.. 2.Ke4 and now A) 2...Bh3 3.Kf4 Ke7 (3...Bg2 4.e6+ Kd6 5.Bb4+ Kxd5 6.e7+-) 4.Bb4+ Kd7 5.Kg5 Bg2 6.e6+; B) 2...Ke7 3.Bb4+ Kd7 4.Kf4 Bh3 5.Kg5]
In an opposite coloured bishops ending, two split pawns up, the ideas to remember are:
a) the further apart the pawns are, the greater the chance of winning;
b) only one file apart, the pawns cannot win;
c) to win, the stronger side's king must be able to break through to support the advance of one of the pawns; the defending side must try to prevent this.
1.Kd5 Kf6! 2.Bg4 Bg3! [2...Ke7? 3.Ke4 Kd6 4.Bd7 Ke7 5.f4 Kf6 6.f5 Ke7 7.Kd5 Kf6 8.Kc5 Ke7 9.Kb5 Kf6 10.Ka6 Ke7 11.Kb7 Kd8 12.f6 Bd6 13.f7] 3.Kc5 Bc7! 4.Kb5 Ke7 5.Ka6 Kd8 6.Kb7 Bf4 White can make no progress. =
We have now covered the basics of opposite coloured bishops in the endgame, which, as we have seen, can often present drawing chances to the weaker side.
(Main sources: Averbakh/Mednis)
In the middlegame it is a different story altogether. In the middlegame opposite coloured bishops favour the side with the initiative.(5) King,D - Menzel [C15]
Junior game, 1979
1.e4 e6 2.d4 d5 3.Nc3 Bb4 Opposite coloured bishop middlegames are quite frequent in the Winawer French. 4.Nge2 An interesting way of avoiding main lines, favoured by Lasker.
4...dxe4 5.a3 Bxc3+ [5...Be7 6.Nxe4] 6.Nxc3 Nc6 7.Bb5 Nge7 8.Bg5! f6 9.Be3 0-0 10.Qd2 [White is happy to sacrifice the pawn for development and attacking chances. If 10.Nxe4? f5! (threat f5-f4.)] 10...f5 11.0-0-0 a6 12.Bxc6 Nxc6 13.Bf4
[A typical position in this line; Black has decided to hold his extra pawn with f7-f5; the price he pays is a weakness on the dark squares. White must open a file so that his heavy pieces can combine with his powerful unopposed bishop.] 13...Ne7 [13...b5 14.d5! Ne7 15.dxe6 Bxe6 16.Qxd8 Rfxd8 17.Bxc7+/- (King.)] 14.f3! exf3 15.gxf3 Ng6? 16.Bg5 Qd6 17.h4! [In positions with opposite-sides castling, whoever gains the initiative is likely to win; exactly the same is true of middle-games with opposite-coloured bishops. In this position, therefore, attack is more important than material.] 17...Rf7 [Black takes precautions against the coming attack against g7.] 18.h5 Nf8 19.Bf4 Qd8 20.Rdg1 Nd7 21.Rg3 Nf6 22.Be5 [White probes the Black defenses. He knows he wants to attack g7 but he is not yet sure of his best attacking formation.] 22...Nd7 23.Bf4! [White realises that it is important to keep his powerful dark squared bishop] 23...Nf6 [Black is on the defensive and is happy to repeat moves.] 24.Bg5 [White tries another tack.] 24...Bd7 [Notice that this bishop is helpless to defend the dark squares that will soon be threatened.] 25.Rhg1 Kh8 [How can White strengthen his attack?] 26.Ne2! [Since Black is on the defensive, White realises that the knight is not needed on the queenside for defense; instead it can join in the attack on the king-side.] 26...c5 27.Nf4 h6 [27...Rc8 28.Ng6+! hxg6 (28...Kg8 29.Ne5+-) 29.hxg6 Rf8 30.Rh3+ Kg8 31.Rgh1] 28.Ng6+ Kh7 [28...Kg8 29.Bxh6 Nxh5 30.Rh3 Nf6 31.Bg5 Rf8 32.Rh8+ Kf7 33.Rxf8++-] 29.Ne5 Re7 [29...Rf8 30.Bxh6!] 30.Bxf6 gxf6 31.Qg2! [31.Qg2 Qf8 (31...fxe5 32.Rg7+ Kh8 33.Qg6; 31...Qh8 32.Ng6) 32.Ng6 Qf7 33.Nxe7 Qxe7 34.Rg7+] 1-0
A few years later, a remarkably similar game was played by Britain's first Grandmaster, Tony Miles.
(6) Miles,A - Reefschlager,H [C15]
1.e4 e6 2.d4 d5 3.Nc3 Bb4 4.Nge2 dxe4 5.a3 Bxc3+ 6.Nxc3 Nc6 7.Bb5 Nge7 8.Bg5! f6 9.Be3 0-0 10.Qd2 [White is happy to sacrifice the pawn for development and attacking chances.] 10...a6 11.Bxc6 Nxc6 12.0-0-0 f5?! [This is probably too greedy. Black weakens his black squares, which is just what White wants, since it makes his bishop a very dangerous piece - it has no opponent!] [12...b6 13.Nxe4 Bb7 14.Qd3] 13.Bg5 Qe8 14.f3! [White opens lines to enable his rooks to fire at the Black king.] 14...exf3 15.gxf3 Nd8 16.Rhg1!
[Simple chess; White intends to double rooks on the g-file and then point his bishop at g7. Notice that the Black bishop is unable to help in the defence.] 16...c6 17.Rg3 Rf7 18.Rdg1 b5 19.Bf6! [Black is already in deep trouble.] 19...Raa7 [19...Rxf6 20.Rxg7+ Kh8 21.Qg5 Rg6 (21...Rf8 22.Rxh7+ Kxh7 23.Qh4+) 22.Rxg6 hxg6 23.Qh6++-] 20.Qh6 Qf8 21.Be5! [Withdrawing the powerful bishop to a safer firing point.] 21...Kh8 22.Rh3! Qg8 23.Ne2! [Bringing up the reserves; the plan is simply Ne2-f4-g6.] 23...f4 24.Rxg7! Rxg7 25.Nxf4 Nf7 26.Ng6#
A lovely finish! 1-0