Chess is a two-player strategy board game of pure skill and one of the deepest and most complex games commonly played. The number of legal positions in chess is estimated to be between 1043 and 1050, and the game-tree complexity[?] approximately 10123. Chess is played both recreationally and competitively in clubs[?], tournaments, on-line, and by mail (correspondence chess).
Chess is played on a square board divided into 64 squares upon which move 16 "white" and 16 "black" pieces. Sets used for play are commonly made of wood or plastic, although ornamental sets of stone, glass, or metal are often used to decorate homes.
Chess originated from the Indian game Chatrang, about 1400 years ago. The game is related to xiangqi (象棋, Chinese Chess) in China, and Shogi in Japan. It reached Russia via Mongolia, where it was played at the beginning of the 7th century. From India it migrated to Persia, and spread throughout the Islamic world after the Muslim conquest of Persia. It was introduced into Spain by the Moors in the 10th century, where a famous games manuscript covering chess, backgammon, and dice named the Libro de los juegos, was written under the sponsorship of Alfonso X of Castile during the 13th century. Chess reached England in the 11th century, and evolved through various versions such as Courier.
By the end of the 15th century, the modern rules for the basic moves had been adopted: pawns gained the option of moving two squares on their first move; bishops could move arbitrarily far along an open diagonal (previously being limited to a move of exactly two squares diagonally, jumping over the intervening square), and the queen was allowed to move arbitrarily far in any direction, making it the most powerful piece. (Before, she could only move one square diagonally.) There were still variations in rules for castling and the outcome in the case of stalemate.
These changes collectively helped make chess more open to analysis and thereby develop a more devoted following. The game in Europe since that time has been almost the same as is played today. The current rules were finalized in the early 19th century, except for the exact conditions for a draw.
Staunton styled himself the first World Champion of Chess in the 1850s; however he avoided matches against the strongest competitors of his day, most notably American genius Paul Morphy. The first player to stake a widely recognized claim to being World Champion was Wilhelm Steinitz in 1866.
The World Chess Federation (FIDE) was founded in 1924. When the reigning World Champion Alexandre Alekhine died in 1946, FIDE took over the function of organizing World Championship matches. Before that time, sitting champions had been somewhat capricious in determining against whom and on what terms they would accept a challenge match. FIDE also assumed the role of awarding the titles Grandmaster and International Master, as well as eventually assigning numerical ratings to players.
In 1993, in the middle of a cycle of matches to determine the World Champion, Garry Kasparov and Nigel Short broke with FIDE to organize their own match for the title. They complained of corruption and a lack of professionalism within FIDE, and formed a competing Professional Chess Association[?]. Since then there have been two simultaneous World Champions and World Championships: one extending the Steinitzian lineage in which the current champion plays a challenger in match format (a series of many games); the other following FIDE's new format of a tennis-style elimination--or "Knockout"--tournament with dozens of players competing.
Once considered only a curiosity, computer chess programs have risen in ability to the point where they can seriously challenge human grandmasters.
Kasparov, then ranked number one in the world, played a six-game match against IBM's chess computer Deep Blue in 1996 and won. The six-game rematch in 1997 was won by the machine which was subsequently retired by IBM. In October, 2002, Vladimir Kramnik drew in an eight-game match with the computer program Deep Fritz. In February, 2003, Gary Kasparov drew a six game match with the computer program Deep Junior.
In May 2002, several leaders in the chess world met in Prague and signed a unity agreement which should ensure the crowning of an undisputed world champion by 2003, and restore the traditional cycle of qualifying matches by 2005. The semifinalists for the 2003 championship are Vladimir Kramnik vs. Peter Leko[?], and Ruslan Ponomariov[?] vs. Gary Kasparov.
At one time, chess games were recorded using Descriptive chess notation, a somewhat clumsy notation that takes more space, more time to say, and more time to explain than its replacement, algebraic chess notation. Portable Game Notation (PGN) is the most common standard computer-processable format for recording chess games, and is based on algebraic chess notation.