Chess

Chess is a two-player abstract strategy board game for players that is played on a checkered board. The chessboard is divided into an 8 by 8 grid of 64 squares of alternating color. Each player controls sixteen pieces of six types on a chessboard.

The object of the game is to checkmate the opponent’s king; checkmate occurs when a king is threatened with capture and has no escape. A game can end in various ways besides checkmate: a player can resign, and there are several ways a game can end in a draw. Each type of piece moves in a distinct way, and the rules governing the play of the game are set by FIDE (Fédération Internationale des Échecs), the international governing body for chess.

## History

The history of chess can be traced back nearly 1,500 years to its earliest known predecessor, called chaturanga, in India. The game was modified in terms of shapes and rules and developed into Shatranj in Persia. Following the Arab invasion and conquest of Persia, chess was taken up by the Muslim world and subsequently spread to Europe via Spain and Italy. The game evolved roughly into its current form by about 1500 CE.

During the late 18th century to the 1880s, “Romantic chess” was the predominant playing style. Chess games of this period emphasized quick, tactical maneuvers rather than long-term strategic planning. The Romantic era of play was followed by the Scientific, Hypermodern, and New Dynamism eras. In the second half of the 19th century, modern chess tournament play began, and the first official World Chess Championship was held in 1886. The 20th century saw great leaps forward in chess theory and the establishment of the World Chess Federation. In 1997, an IBM supercomputer beat Garry Kasparov, the then world chess champion, in the famous Deep Blue versus Garry Kasparov match, ushering the game into an era of computer domination. Since then, computer analysis has contributed to much of the development in chess theory and has become an important part of preparation in professional human chess. Later developments in the 21st century made the use of computer analysis far surpassing the ability of any human player accessible to the public. Online chess, which first appeared in the mid-1990s, also became popular in the 21st century.

## Rules

The rules of chess are published by FIDE (Fédération Internationale des Échecs, "International Chess Federation"). The chess pieces are divided into two sets, usually light and dark colored, referred to as *white* and *black*. The players of the sets are referred to as *White* and *Black*, respectively. Each set consists of sixteen pieces: one king, one queen, two rooks, two bishops, two knights, and eight pawns.

The game is played on a square board of eight rows (called *ranks*) and eight columns (called *files*). By convention, the 64 squares alternate in color and are referred to as *light* and *dark* squares; although the actual colors may vary.

The pieces are set out as shown in the diagram below:

Thus, on White's first rank, from left to right, the pieces are placed as follows: rook, knight, bishop, queen, king, bishop, knight, rook. Eight pawns are placed on the second rank. Black's position mirrors White's, with an equivalent piece on the same file. The board is placed with a light square at the right-hand corner nearest to each player. The correct positions of the king and queen may be remembered by the phrase "queen on her own color" (i.e. the white queen begins on a light square, and the black queen on a dark square).

In competitive games, the piece colors are allocated to players by the organizers; in informal games, the colors are usually decided randomly, for example by a coin toss, or by one player concealing a white pawn in one hand and a black pawn in the other, and having the opponent choose.

White moves first, after which players alternate turns, moving one piece per turn (except for castling, when two pieces are moved). A piece is moved to either an unoccupied square or one occupied by an opponent's piece, which is captured and removed from play. With the sole exception of *en passant*, all pieces capture by moving to the square that the opponent's piece occupies. Moving is compulsory; a player may not skip a turn, even when having to move is detrimental.

* The king moves one square in any direction. There is also a special move called *castling* that involves moving the king and a rook. The king is the most valuable piece—attacks on the king must be immediately countered, and if this is impossible, the game is immediately lost.
* A rook can move any number of squares along a rank or file, but cannot leap over other pieces. Along with the king, a rook is involved during the king's castling move.
* A bishop can move any number of squares diagonally, but cannot leap over other pieces.
* A queen combines the power of a rook and bishop and can move any number of squares along a rank, file, or diagonal, but cannot leap over other pieces.
* A knight moves to any of the closest squares that are not on the same rank, file, or diagonal. (Thus the move forms an "L"-shape: two squares vertically and one square horizontally, or two squares horizontally and one square vertically.) The knight is the only piece that can leap over other pieces.
* A pawn can move forward to the unoccupied square immediately in front of it on the same file, or on its first move it can advance two squares along the same file, provided both squares are unoccupied (black dots in the diagram). A pawn can capture an opponent's piece on a square diagonally in front of it by moving to that square (black crosses). It can*not* capture a piece while advancing along the same file. A pawn has two special moves: the *en passant* capture and promotion.