exchange of knights is acceptable for the stronger side. However, the exchange of knights may benefit the defender, especially if there is only one passed pawn and he has no other weaknesses. This endgame occurs in about 0.6% of games between high-rated players. Rook If each side has a rook in addition to the bishop, the stronger side has many more winning prospects. The attacking rook can have influence on both colors of squares. Sometimes exchanging the rook for the defender's bishop breaks a fortress. Sometimes the defending bishop can be sacrificed for pawns to result in a rook and bishop versus rook endgame that can be drawn. The most difficult problem encountered by the stronger side is usually in breaking a blockade by the opposite bishop. These endgames occur in 2.8% of the games between high-rated players. Example This type of endgame was reached in a 2006 game between Veselin Topalov and Levon Aronian, see the first diagram. (The game and analysis is on this page and the game score is also here.) White was able to make slow progress (see the second diagram, showing the position after 72 moves). The game concluded: 73. Rd4! Be6+ 74. Kf8 Ra8+ 75. Bd8 Bg4 76. c6 1–0 Black resigned because the pawn will advance to c7 and Black cannot defend against rook attacks on the seventh rank and the h-file. Queen When each side has an additional queen, the possibility of exchanging them is a paramount concern. The stronger side should try to get two widely spaced passed pawns before exchanging queens. Defending squares of the color of the stronger side's bishop can be difficult if there are weaknesses or threats on both sides of the board. The stronger side must increase his advantage before exchanging queens and sometimes this is done with a direct attack on the king. These endgames occur in 0.8% of the games between high-rated players. History The earliest opposite-colored bishop endgame in the ChessBase database is an 1862 game between Louis Paulsen and Adolf Anderssen in their unofficial world championship match. It was a draw because of the wrong rook pawn. Play continued: 55. Bf5+ Kh2 56. Bc2 h4 57. Be4 ½–½ This 1620 game between an unknown player and Gioachino Greco was won by Black on move 50. Quotes "In endings with bishops of opposite color, material means NOTHING, position EVERYTHING." — Cecil Purdy (emphasis