the theory of chess
Chess has an extensive literature. In 1913, the chess historian H.J.R. Murray estimated the total number of books, magazines, and chess columns in newspapers to be about 5,000. B.H. Wood estimated the number, as of 1949, to be about 20,000. David Hooper and Kenneth Whyld write that, "Since then there has been a steady increase year by year of the number of new chess publications. No one knows how many have been printed." Significant public chess libraries include the John G. White Chess and Checkers Collection at Cleveland Public Library, with over 32,000 chess books and over 6,000 bound volumes of chess periodicals; and the Chess & Draughts collection at the National Library of the Netherlands, with about 30,000 books.
Chess theory usually divides the game of chess into three phases with different sets of strategies: the opening, typically the first 10 to 20 moves, when players move their pieces to useful positions for the coming battle; the middlegame; and last the endgame, when most of the pieces are gone, kings typically take a more active part in the struggle, and pawn promotion is often decisive.
Opening theory is concerned with finding the best moves in the initial phase of the game. There are dozens of different openings, and hundreds of variants. The Oxford Companion to Chess lists 1,327 named openings and variants.
Middlegame theory is usually divided into chess tactics and chess strategy. Chess strategy concentrates on setting and achieving long-term positioning advantages during the game – for example, where to place different pieces – while tactics concerns immediate maneuver. These two aspects of the gameplay cannot be completely separated, because strategic goals are mostly achieved through tactics, while the tactical opportunities are based on the previous strategy of play.
Endgame theory is concerned with positions where there are only a few pieces left. Theoretics categorize these positions according to the pieces, for example "King and pawn endings" or "Rook versus a minor piece".
