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A game of strategy for two players that probably originated in India, though the earliest documentary references are in Chinese and Persian texts in about AD 600. Each player has 16 pieces, either black or white, consisting of eight pawns, two rooks (also known as castles), two knights, two bishops, a queen, and a king. The object is to lay siege to the opposing king in such a way that it cannot escape attack – a position known as checkmate (from the Persian phrase "Shah Mat," meaning "the king is dead"). There is no element of chance in a game of chess and skill is the determinant of victory.

There are 400 first move combinations – 20 for white × 20 for black (though only 64 of these are regarded as strong), 318,979,564,000 ways of playing the first four moves, and 169,518,829,100,544,000,000,000,000,000 ways of playing the first ten moves. The total number of possible board configurations is estimated at 10120; for comparison, that of Go is generally put at about 10174.

A standard chessboard is a square plane divided into 64 smaller squares by straight lines at right angles. Originally, it wasn't checkered (that is, made with its rows and columns alternately of dark and light colors), and this feature was introduced merely to help the eye in actual play. In many puzzles based on chess the utility of checkering is questionable, and the board may be generalized to any n × n size.

One of the first puzzles to use a chessboard was the wheat and chessboard problem, posed in 1256 by the Arabic mathematician Ibn Kallikan. Among the earliest problems to involve chess pieces, due to Guarini di Forli in 1512, asks how two white and two black knights can be interchanged, using normal knight's moves, if they are placed at the corners of a 3 × 3 board. The unusual L-shaped movement of the knight is what makes one of the best known chess puzzles, the knight's tour, such a challenge. Other standard puzzles, often called simply the kings problem, the queens problem, the rooks problem, the bishops problem, and the knights problem, ask for the greatest number of each of these pieces that can be placed on an 8 × 8 board or on a generalized n × n board without attacking each other, and/or the smallest number of each of these pieces are needed to occupy or attack every square. Fairy chess is any variant on the standard game, which may involve a change in the form of the board, the rules of play, or the pieces used. For example, the normal rules of chess can be used but with a cylindrical or Möbius band connection of the edges.

Origins of chess

Chess has been attributed to some 14 different ethnic groups, although most scholars think India was its birthplace. It probably passed through Persia to Europe. Its name is from Old French, from the Hindu chaturanga, which refers to the components of an army: horses, elephants, chariots, and infantry. Its relation to warfare is seen in the Buddhist story that Buddhism invented it instead of war.

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