Wrong bishop

A wrong bishop is a bishop that travels on the wrong color for a particular task. The best-known case occurs when it supports a rook pawn, meaning a pawn on an edge file, but cannot control the corner where that pawn must promote.

If the defending king reaches that corner, the bishop cannot check it or force it out. The attacking king cannot move illegally next to the enemy king either. In the elementary ending of king, bishop, and wrong rook pawn versus king, this limitation usually creates a drawing fortress, a defensive setup the stronger side cannot break.

Wrong is relative to the objective, not a general judgment of the bishop. The same bishop may be active and attack several pawns while still missing the one required square. It should not be confused with a bad bishop, whose movement is restricted by its own pawns on the same color.