Opposite-colored bishops endgame

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 cannot 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. With additional pieces, the stronger side has more chances to win, but not as many as if the bishops were on the same color.

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 an advantage of two or even three pawns, since the weaker side can create a blockade on the squares on which his bishop operates.

Edmar Mednis gives two principles for endgames with bishops on opposite colors:

Ian Rogers gives three principles when there are only the bishops and pawns:

In endings with opposite-colored bishops, a material advantage is less important than in most endgames and position is more important. Positions when one side has an extra pawn are usually drawn and even two extra pawns (and occasionally more) may not be enough to win (Nunn 2007:145ff). 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% are won if the bishops are on the same color.)

Zugzwang is a tool that often helps the superior side win an endgame. It is a fairly common occurrence in endings with bishops on the same color but is much less common in endgames with opposite-colored bishops (Angos 2005:84,95).

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).

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