Chess, sometimes also known as international chess, is a board game and mental-skill game for two players. It is played on a square board of eight rows (called ranks) and eight columns (called files), giving 64 squares of alternating colour, light and dark, with each player having a light square at the bottom right when facing the board. Each player begins the game with 16 pieces that each move and capture other pieces on the board by defined directions and in some instances, limited range: eight pawns, two knights, two bishops, two rooks, one queen and one king. One player (who is always first to move) controls the white pieces; the other player controls the black pieces. In chess, when a player's king is directly attacked by one or more of the opponent's pieces, the player is said to be in 'check'. When in check, only moves that can evade check or block check are permitted. The object of the game is to checkmate the opponent; this occurs when the opponent's king is in check, and no move can be made that would escape from check.

Introduction

Chess is not a game of chance; it is based solely on tactics and strategy. Nevertheless, the game is so complex that not even the best players can consider all contingencies: although only 64 squares and 32 pieces are on the board, the number of possible games that can be played far exceeds the number of atoms in the universe (see Shannon number).

Chess is one of the world's most popular games; it has been described not only as a game but also as an art or science. Chess is sometimes seen as an abstract wargame; as a "mental martial art", and teaching chess has been advocated as a way of enhancing mental prowess. Chess is played both recreationally and competitively in clubs, tournaments, online, and by mail (correspondence chess). Many variants and relatives of chess are played throughout the world. The most popular, in descending order by number of players, are Xiangqi (in China), Shogi (in Japan), and Janggi (in Korea).


Many countries claim to have invented the chess game in some incipient form. The most commonly held belief is that chess originated in India, where it was called Chaturanga, which appears to have been invented in the 6th century AD. Although this is commonly believed, it is thought that Persians created a more modern version of the game after the Indians. In fact, the oldest known chess pieces have been found in excavations of ancient Persian territories.

Another theory exists that chess arose from the similar game of Chinese chess, or at least a predecessor thereof, existing in China since the 2nd century BC. Joseph Needham and David Li are two of many scholars who have favored this theory.

Chess eventually spread westward to Europe and eastward as far as Japan, spawning variants as it went. One theory suggests that it migrated from India to Persia, where its terminology was translated into Persian, and its name changed to chatrang. The entrance of chess into Europe, notably, is marked by a massive improvement in the powers of the queen. The oldest known texts describing chess seem to indicate a bi-directional spread from the Persian empire. In fact, the oldest known reference points to Shah Ardashir as being a master of the game, his rule was from 224 - 241 AD. This would indicate that chess was invented some time before his rule.

From Persia it entered the Islamic world, where the names of its pieces largely remained in their Persian forms in early Islamic times. Its name became shatranj, which continued in Spanish as ajedrez and in Greek as zatrikion, but in most of Europe was replaced by versions of the Persian word shāh = "king".

There is a theory that this name replacement happened because, before the game of chess came to Europe, merchants coming to Europe brought ornamental chess kings as curiosities and with them their name shāh, which Europeans mispronounced in various ways.

checkmate: This is the English rendition of shāh māt, which is Persian for "the king is finished". 
rook: From the Persian rukh, which means "chariot", but also means "cheek" (part of the face). The piece resembles a seige tower. It is also believed that it was named after the mythical Persian bird of great power called the roc. 
bishop. From the Persian pīl means "the elephant", but in Europe and the western part of the Islamic world people knew little or nothing about elephants, and the name of the chessman entered Western Europe as Latin alfinus and similar, a word with no other meaning (in Spanish, for example, it evolved to the name "alfil"). This word "alfil" is actually the Arabic for "elephant" hence the Spanish word would most certainly have been taken from the Islamic provinces of Spain. The English name "bishop" is a rename inspired by the conventional shape of the piece. In Russia, the piece is, however, known as слон = "elephant". 
queen. Persian farzīn = "vizier" became Arabic firzān, which entered western European languages as forms such as alfferza, fers, etc but was later replaced by "queen". 
The game spread throughout the Islamic world after the Muslim conquest of Persia. Chess eventually reached Russia via Mongolia, where it was played at the beginning of the 7th century. It was introduced into Spain by the Moors in the 10th century, and described in a famous 13th century manuscript covering chess, Chess, and dice named the Libro de los juegos. Chess also found its way across Siberia into Alaska. 

Rules of chess

When a game of chess begins, one player controls the sixteen black pieces while the other uses the white pieces. The colors are chosen either by a friendly agreement (a game of chance) or by a tournament director[1]. White always moves first and therefore has a slight advantage over black. The chess pieces should be set up on a standard chessboard with a white square in the bottom right hand corner.

Each chess piece moves a different way. The rook moves along horizontal and vertical lines, while the bishop moves in diagonal lines of the same color. The queen is a combination of the rook and bishop (it can move diagonally, horizontally and vertically). The knight can jump over occupied squares and moves in an L shape. Pawns can move forward just one square at a time (they can move two squares if they have not moved off their starting square). Pawns are unusual because they attack diagonally and not in the direction of movement. The king is the most important piece, yet it can only move to an adjacent or diagonally adjacent square.

When a piece is captured (or taken), the attacking piece moves towards and replaces the enemy piece on its square (en passant being the only exception). The king cannot be captured in regular chess, only put in check. If a player is unable to get their king out of check it is called checkmate and the game is over.

Chess games do not have to end in checkmate. Often at the higher level of chess, games end in a draw (tie). A draw can occur under many situations including: mutual agreement to draw, stalemate, threefold repetition or the fifty move rule.

Strategy and tactics For more details on this topic, see Chess strategy and tactics. Chess openings are a sequence of moves, often memorized, which will help a player build up their position and prepare for the middlegame. Openings are often designed to take hold of the center of the board (e4, e5, d4 and d5), develop pieces, protect the king and create a strong pawn structure. Hypermodernism advocates the control of the center not by using pawns but with distant pieces. It is often important for a player to castle (a special move that moves the king from the center of the board two squares towards one of the corners) to protect the king. See the list of chess openings for more information.

The black knight on e6 is pinned to its king by the white bishop and the white knight is pinned to the queen on b1. When taking and trading pieces in chess the chess piece point values becomes important. Valuations differ slightly from book to book, but generally, queens are worth 9 points, rooks are worth 5, bishops and knights are worth 3 and pawns are worth 1. Since the king's loss ends the game it is invaluable. The actual value and importance of a piece will vary based upon the position. If a player performs a sacrifice (e.g. exchange sacrifice), they are choosing to ignore the standard valuation of their pieces for positional or tactical gains.

A few positional elements are common to most chess tactics are forks and traps. A fork is a situation where a piece is moved such that it is attacking (forking) two other pieces simultaneously. It usually is difficult for the other player to protect both of their pieces in one move. Pins are used to prevent the movement of an enemy piece by threatening any pieces behind it should it move. Skewers are a kind of reverse pin where the more valuable piece is placed in front of a less important one. A discovered attack is an attack where a piece moves and uncovers a line for another piece which does the attacking. Other tactical elements include: zwischenzug, undermining, overloading and interference.

During the endgame pawns and kings become relatively more powerful pieces as both sides often try to promote their pawns. If one player has a large material advantage checkmate may happen quickly in the endgame, but if the game is relatively even tablebases and endgame study are essential. Controlling the tempo (time used by each move) becomes especially important when fewer pieces are left on the board. In some cases, a player will have a material advantage, but will not have enough material to force a checkmate.

[edit] Gameplay variations Besides the standard version of chess, there are some common variations in the gameplay.

Blitz chess is a version of chess where a chess clock is used to limit the time control for each player. Generally each side has three to fifteen minutes (five is common) for all of their moves. An even faster version of chess is known as bullet chess or lightning chess. Bullet chess's time controls are less than three minutes. Speed chess requires the player to spend less time thinking because if the player's time runs out they lose. When playing at faster time controls computers become relatively more powerful to humans.

When two players are separated by great distances they can still play chess. Correspondence chess is chess played through the mail, e-mail or special Correspondence Chess Servers. Today, chess is often played on the internet through the Internet Chess Club, Yahoo! Games or another host.

There are also game variants on rules and number of players, i.e. "Bughouse" Chess is a type of chess played with two boards, and two teams of two players using opposite colored pieces. Bughouse Chess retains the rules of piece movement and checkmate but gives the player the option to give up the turn of moving a piece in return for adding a piece captured by their opponent. For more information, please see Bughouse Chess.

Modern chess

A typical Staunton-design set and clockEarly on, the pieces in European chess had limited movement; bishops could only move by jumping exactly two spaces diagonally (similar to the elephant in xiangqi), the queen could move only one space diagonally, pawns could not move two spaces on their first move, and there was no castling. By the end of the 15th century, the modern rules for the basic moves had been adopted from Italy: pawns gained the option of moving two squares on their first move and the en passant capture therewith, bishops acquired their modern move, and the queen was made the most powerful piece; consequently modern chess was referred to as "Queen's Chess" or "Mad Queen Chess." 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.

The most popular piece design, the "Staunton" set, was created by Nathaniel Cook in 1849, endorsed by Howard Staunton, a leading player of the time, and officially adopted by Fédération Internationale des Échecs (FIDE) in 1924.

Chess's international governing body is FIDE, which has presided over the world championship matches for decades. See World Chess Championship for details and a more in-depth history. Most countries of the world have a national chess organization as well. Although chess is not an Olympic sport, it has its own Olympiad, held every two years as a team event.

Notation Until the 1970s, at least in English-speaking countries, chess games were recorded and published using descriptive chess notation. This has been supplanted by the more compact algebraic chess notation. Several notations have emerged, based upon algebraic chess notation, for recording chess games in a format suitable for computer processing. Of these, Portable Game Notation (PGN) is the most common. Apart from recording games, there is also a notation Forsyth-Edwards Notation for recording specific positions. This is useful for adjourning a game to resume later or for conveying chess problem positions without a diagram.

Computer chess Main article: Computer chess Serious work on machines that play chess has been going on since 1890, and chess-playing computer programs featured prominently in the artificial intelligence boom of the 1950s - 1970s. At first considered only a curiosity, the best chess playing programs — like Shredder, Fritz etc. — have become extremely strong players. In blitz chess, they can beat the best human players; at regular time controls, however, battles between the very best chess programs and the very best human players have been tantalizingly finely balanced. However, it is important to note that the method by which computer programs play chess does not really resemble the way humans play chess — the computer basically just calculates the board position after every possible combination of legal moves and acts accordingly, whereas human masters act more from intuition and pattern recognition. Moreover, as CPU speed and memory become less expensive, computer chess programs can search ever larger numbers of moves in the same amount of time, and store ever larger databases of opening and endgame positions. Nor has the study of chess proven particularly useful in the broader AI field; the methods used to play high-level chess are very different to the ones used for machine learning, machine vision, and the like.

Garry Kasparov, then ranked number one in the world, played a six-game match against IBM's chess computer Deep Blue in February 1996. Deep Blue shocked the world by winning the first game in Deep Blue - Kasparov, 1996, Game 1, but Kasparov convincingly won the match by winning three games and drawing two.

The six-game rematch in May 1997 was won by the machine (informally dubbed Deeper Blue) which was subsequently retired by IBM. In October 2002, Vladimir Kramnik drew in an eight-game match with the computer program Deep Fritz. In 2003, Kasparov drew both a six-game match with the computer program Deep Junior in February, and a four-game match against X3D Fritz in November.

The chess machine Hydra is the intellectual descendant of Deep Blue; and appears to be somewhat stronger than Deep Blue was. Certainly it is very much comparable in terms of positions analysed per second. Given the relative ease with which it beats the other programs, and the humans it has met, Hydra may be expected to beat any unaided human player in match play. In June 2005, Hydra scored a decisive victory over the then 7th ranked GM Michael Adams winning five games and drawing one game in a six game match. Whilst too few games have been played to establish this, and neither Kramnik or Kasparov have played Hydra, Hydra's creators estimate its rating should be over 3000.

Kasparov's loss to Deep Blue has inspired the creation of chess variants in which human intelligence can still overpower computer calculation. In particular Arimaa, which is played upon a standard 8×8 chessboard, is a game at which humans can beat the best efforts of programmers so far, even at fast time controls.

Chess variants For more details on this topic, see Chess variant. Chess variants are forms of chess where the game is played with a different board, special fairy pieces or different rules. There are over 1500 unique variants of chess. Bobby Fischer noted the overemphasis on memorizing chess openings in normal chess and invented Fischer Random Chess. Fischer Random Chess and other versions with different starting positions work by scrambling the initial starting position for every game. See the list of chess variants for more details.

See also Demonstration (sample) chess game explains chess through a simple demonstration Chess terminology Chess problems and puzzles Ways to play chess: Correspondence chess, Blitz chess, Bullet chess, Chess handicap, Simultaneous chess, Blindfold chess, Human chess Internet servers to play chess: Internet Chess Club, FICS, InstantChess.com, ChessWorld.net ELO rating system Administrative bodies: FIDE English Chess Federation United States Chess Federation Chess symbols in Unicode Chess and mathematics Chess as mental training Chess-related deaths List of chess players List of chess topics List of national chess championships [edit] Famous chess games Bowdler - Conway, London, 1788, the first example of the famous double rook sacrifice; The immortal game between Adolf Anderssen and Lionel Kieseritzky (1851); The evergreen game between Adolf Anderssen and Jean Dufresne (1852); The opera game between Paul Morphy and two allies, the Duke of Brunswick and Count Isouard (1858); Lasker - Bauer, Amsterdam, 1889, the first example of the famous double bishop sacrifice; The Game of the Century between Bobby Fischer and Donald Byrne (1956); The Match of the Century between Bobby Fischer and Boris Spassky (1972); Deep Blue - Kasparov, 1996, Game 1, the first game in which a chess-playing computer defeated a reigning world champion using normal time controls (1996); Deep Blue - Kasparov, 1997, Game 6, the last game of the 1997 rematch, which Deep Blue won, making it the first computer to defeat a world champion in a match over several games; Kasparov versus The World, in which the reigning world champion played, via the Internet, against the entire rest of the world in consultation (1999); Kasparov - Topalov, Wijk aan Zee, 1999, rook sacrifice with a 15+ moves forced sacrificial combination. One of the most commented chess games ever, with extensive press coverage. [edit] History of chess Timeline of chess World Chess Championship Greatest chess player of all time Origins of chess Chess in early literature Early arabic chess literature Cox-Forbes theory Chess in Europe Chess During World War II Chess Olympiad World records in chess [edit] World chess champions Main article: World Chess Championship Unofficial but widely recognized as Champions (pre-championship era):

Philidor Howard Staunton Adolf Anderssen Paul Morphy Official Champions:

Wilhelm Steinitz Emanuel Lasker José Raúl Capablanca Alexander Alekhine Max Euwe Mikhail Botvinnik Vassily Smyslov Mikhail Tal Tigran Petrosian Boris Spassky Robert Fischer Anatoly Karpov Garry Kasparov Unofficial but widely accepted as current World Champion:

Vladimir Kramnik FIDE World Champions after Garry Kasparov:

Alexander Khalifman Vishwanathan Anand Ruslan Ponomariov Rustam Kasimdzhanov Veselin Topalov [edit] Chess literature Chess columns in newspapers Chess libraries Collections of Chess Games Opening Manuals [edit] Chess in the arts and literature Through the Looking-Glass Searching for Bobby Fischer The Luzhin Defence The Royal Game by Stefan Zweig Chess and music Checkmate, a ballet by the composer Arthur Bliss The Lewis chessmen also inspired Noggin the Nog. Harry Potter and the Philosopher's Stone Knight Moves The Seventh Seal 2001: A Space Odyssey Chess, a musical by Tim Rice and ABBA The Eight by Katherine Neville (1998) The Flanders Panel by Arturo Perez-Reverte The Tower Struck By Lightning by Fernando Arrabal Fresh, a 1994 film All the King's Horses, a short story by Kurt Vonnegut from 'Welcome to the Monkey House.' Striding Folly, a short story by Dorothy L. Sayers (1939) [edit] References Hooper, David and Whyld, Kenneth (1992). The Oxford Companion to Chess, 2nd Edition, Oxford University Press. ISBN 0198661649. Reprint: (1996) ISBN 0192800493 Mason, James (1947). The Art of Chess, Dover Publications. ISBN 486204634. (see the included supplement, "How Do You Play Chess") Rizzitano, James (2004). Understanding Your Chess, Gambit Publications. ISBN 1904600077. Tarrasch, Siegbert (1994). The Game of Chess. Algebraic Edition, Hays Publishing. ISBN 1880673940. Wolff, Patrick (1991). The Complete Idiot's Guide to Chess, 3rd Edition, Alpha Books. ISBN 1592573169. [edit] External links Find more information on Chess by searching one of Wikipedia's sibling projects: Wiktionary (a free dictionary) Wikibooks (free textbooks) Wikiquote (quotations) Wikisource (a free library) Commons (images and media) Wikinews (news stories) [edit] General The Pushed Pawn game databases articles chess politics forums Opening Theory in the Chess Wikibook Official FIDE Website Official FIDE rules Official ECU Website Chessbase News British Chess Magazine Solve interactive chess problems linkcollection to free downloadable chessgames Online Chess server myChess.de Free Online chess(turn based) Free Online chess (turn based) Queen Alice Internet Chess Club - Play internet based correspondence chess Online chess database and community Challenge the computer at Chess Chess.FM - Annotated Grandmaster games and tutorials The Chess Variants Pages Chess curiosities by Tim Krabbé Bill Wall's Chess Page Ed's Ever-Growing Chess Page - essays, problems, cartoons, limericks, games, photos, puzzles, etc. WikiTeX chess - Supports editing chess games directly in Wiki articles. Play chess online instantly Play chess online Chess Webmaster Tools PlayerPlaza Chess - Play competitive head-to-head match play International Computer Games Association GameKnot online chess - one of the largest turn-based online chess communities Play Online Free Chess game - The Only Free Online Chess Game and Download site. Art of Chess Pitt Chess Archives http://www.accoonachess.com/ get the latest on chess news and also play the chess A.I. which learns from every game it plays! How To Play Chess. For Beginners and Parents. Photos of chess boards and pieces. Free photos for use in chess publications and websites. Begin Chess - Beginners' chess blog. [edit] Games for download. Mostly in SCID,PGN, or CBF.

http://www.chesslive.de/ Online for games filtered by year, player, opening, etc.. http://www.chesslab.com Search by opening, player, results, position etc. http://www.notzai.com/notzai/regence/regence.shtml Games categorized by ECO codes. (French) http://www.chesscenter.com/twic/twic.html The Week in Chess. Find the latest Games. http://www.chesslib.no/ A Chessbase opening book. ftp://ftp.cis.uab.edu/pub/hyatt/ The resources used by Crafty. http://www.iccf.com/ The International Correspondance Chess Federation's Game Archive. [edit] Free chess software: Programs/Engines/Databases/Utilities Link collection to chess programs Chessopolis: Computer Chess Winboard ChessBase Light Aaron's Chess Engines FAQ [edit] Organizations The International Correspondence Chess Federation U.S. Chess Federation Swedish Chess Computer Federation (Also a collection of games)