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The rook and bishop versus rook endgame is a chess endgame where one player has just a king, a rook, and a bishop, and the other player has just a king and a rook. This combination of material is one of the most common pawnless chess endgames. It is generally a theoretical draw, but the rook and bishop have good winning chances in practice because the defense is difficult. Ulf Andersson won the position twice within a year, once against a grandmaster and once against a candidate master; and grandmaster Keith Arkell has won it 27 times out of 27.[1][2] In positions that have a forced win, up to 59 moves are required.[3] Tony Kosten has seen the endgame many times in master games, with the stronger side almost always winning.[4] Pal Benko called this the "headache ending."[5] David Howell observed, "Especially below elite grandmaster level, this is one of the hardest endgames to draw."[6]
Being a five-piece endgame, the rook and bishop versus rook endgame has been fully analysed using computers. Endgame tablebases show that 40.1% of the legal positions with this material are theoretical wins, but that includes many unnatural positions that are unlikely to occur in games. Edmar Mednis estimated that less than 4% of starting positions that occur in games are theoretical wins.[7]
- ^ (Carlsen & Howell 2023:161)
- ^ In 2007 Giddens (page 78) reported 16 out of 16.
- ^ (Speelman, Tisdall & Wade 1993:382)
- ^ (Kosten 1987:11)
- ^ (Benko 2007:154)
- ^ (Carlsen & Howell 2023:160)
- ^ (Mednis 1996:80)