Opposite-colored bishops: why it's so often a draw

Among all minor-piece endgames, the one where each side has only a single bishop left, on opposite-colored squares, has a very particular reputation: it's known for its drawish tendencies, even with a material imbalance that would be decisive in almost any other endgame.

The mechanism: a color the opponent can never contest

A bishop only ever moves on squares of one color, for the entire game. If White's bishop is light-squared and Black's is dark-squared, neither can ever come challenge the other on its own turf: they simply never cross paths.

In practice, this means the side that's behind can often park its king and bishop on the exact color the opposing pawn needs to promote on, and build a blockade nothing can dislodge: the attacking bishop simply has no way to intervene on that color.

Look at the diagram

Same structure, opposite result

A well-earned reputation, not an absolute rule

Some caution is needed with this reputation: it mostly applies when few pawns remain and no direct attack against the king is possible. With several pawns spread across both wings, or in a position where the kings are exposed, an opposite-colored bishop can instead become a formidable attacking weapon, especially for giving checks on squares the opponent doesn't control. "Often a draw" never means "automatically a draw".

Key takeaways

• ✓A bishop only controls one color of square, for the entire game
• ✓If the two remaining bishops are opposite colors, the side behind can often blockade the opponent's promotion square
• ✓With same-colored bishops, the same material imbalance is generally winning
• ✓This drawish tendency is a reputation, not a guarantee: it depends on how many pawns remain and on king safety