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This article uses algebraic notation to describe chess moves.

The opposite colored bishops endgame is a chess endgame in which each side has a single bishop, but the bishops reside on opposite colored squares on the chessboard, thus can not attack or block each other. Without other pieces (but with pawns) these endings are notorious for their tendency to result in a draw. These are the most difficult endings in which to convert a small material advantage to a win.

Many players in a poor position have saved themselves from a loss by trading down to such an endgame. They are often drawn even when one side has a two or even three pawn advantage since the weaker side can create a blockade on the squares which his bishop operates on. About half of the endings with a bishop and two pawns versus a bishop on the opposite color are drawn (Emms 2004:91). (By contrast, over 90 percent are won if the bishops are on the same color.) Interestingly the weaker side should often try to make his bishop bad by placing his pawns on the same color of his bishop in order to defend his remaining pawns, thereby creating an impregnable fortress (Emms 2004:100). The attacker should generally put his pawns on squares of the opposite color as his bishop to prevent a blockade (Emms 2004:91).

Contents 1 Bishop and pawn versus bishop 2 Bishop and two pawns versus a bishop 2.1 Doubled pawns 2.2 Isolated pawns 2.3 Connected pawns 3 More pawns 4 Example from master game 5 See also 6 References

The attacker's bishop is practically useless and the defender can normally draw if his king can reach any square in front of the pawn that is not of the color of the attacking bishop; or if his bishop can permanently attack any square in front of the pawn (Fine & Benko 2003:184). These endings are trivially drawn 99 percent of the time (Emms 2004:90).

About half of these positions are drawn. In most other endings, a two pawn advantage is usually an easy win. For example, if the bishops were on the same color, 90 percent of the games would be wins.

There are three general cases, depending on the two pawns. In most endings, a pair of connected pawns have the best wining chances, but in these endings a widely-separated pair of pawns have the best chances.

With doubled pawns the position is a draw if the defending king can reach any square in front of the pawns that is not of the color of the attacker's bishop. The second pawn on the file is of no help, so this is like the ending with only one pawn.

With isolated pawns (on different files), the outcome depends on how widely separated the pawns are. The more widely separated they are, the better the winning chances (Emms 2004:95). The rule that holds in most cases is that if only one file separates the pawns the game is a draw, otherwise the attacker wins. The reason is that if the pawns are more widely separated, the defending king must block one pawn while his bishop blocks the other pawn. Then the attacking king can support the pawn blocked by the bishop and win the piece. If only one file is between the pawns, the defender can stop the advance of the pawns. See the diagram (Fine & Benko 2003:184-92). If three files separate the pawns, they normally win (Emms 2004:95).

Positions with connected pawns are the most complex case, and the result depends on the ranks and files of the pawns and the colors and locations of the bishops. If one of the pawns is a rook pawn (on the a file or h file) the position is normally drawn. If the pawns are on the opposite color as the defender's bishop, the defender may be able to blockade the pawns and draw. If both pawns can safely reach the sixth rank, they win (if neither is a rook pawn).

The ideal drawing setup is seen in the diagram at left. Black's king (on a square not of the color of the opposing bishop) and bishop stay two ranks in front of the pawns, with both defending against a pawn advance (here d6 by White) to the same color square as the bishop. The defending bishop must maintain an attack on the pawn on the same color square as itself, so that the attacking king is not allowed to advance. If White pushes the other (unattacked) pawn, Black's bishop sacrifices itself for both pawns, with a draw. In the diagram position, Black on move passes (i.e. a waiting move that maintains the attack on the pawn) with 1... Bb8! 2. Ke4 Bc7! 3. Kf5 Bb8! and so on. White cannot make progress: 4. d6+ is met, as always, by 4... Bxd6 5. exd6+ Kxd6 with an immediate draw; 4. e6 gives Black an unbreakable blockade on the dark squares; and White can never prepare for d6+ by playing Kc5 because Black plays ... Bxe5.

A similar position with White's pawns on the sixth rank is a win because the black bishop has no room to move and maintain the attack on the pawn on d6, thus Black is defeated because of zugzwang. In the position at right, Black loses immediately. Black, on move, must give way with either bishop or king, allowing White to move e7, winning, or else play the hopeless 1... Bxd6 2.Kxd6. If White is to on move in this position, he plays a waiting move such as 1. Kc6, placing Black in the same predicament (1... Ke8 2. Kc7#) (Fine & Benko 2003:184-92).

Draws are possible with more pawns. This is an example of a drawing fortress with opposite-colored bishops when three pawns behind. White simply keeps his bishop on the h3 to c8 diagonal (Dvoretsky 2003:91). (See Fortress (chess)#Fortress with opposite-colored bishops.) Three pawns versus none wins 90 percent of the time (Emms 2004:98).

In Berger versus Kotlerman, the pawns are separated by two ranks, but the game was drawn (Dvoretsky 2003:94).

• 1. Ke2 b3
• 2. Kd1 Kb4
• 3. Bh7 Ka3
• 4. Bg6 Kb2
• 5. Bf7! Ka2
• 6. Be6 Ka3
• 7. Bf5! ½-½

• Endgame

• Dvoretsky, Mark (2003), Dvoretsky's Endgame Manual (first ed.), Russell Enterprises, ISBN 1-888690-19-4

• Emms, John (2004), Starting Out: Minor Piece Endgames, Everyman Chess, ISBN 1-85744-359-4

• Fine, Reuben & Pal Benko (1941, 2003), Basic Chess Endings, McKay, ISBN 0-8129-3493-8