Chess is a strategy game that is played by two people on a checkered board. The board has 64 squares that use alternating colors on an eight-by-eight grid. The game's goal is for one person to trap the opponent's king and make the king's capture unavoidable, which is a condition called "checkmate". Modern chess games may also be played by opponents over a computer. In addition, computers are now capable of playing the game against people. Chess was originally a game played by kings and noblemen. Today, however, it is played by millions of people regardless of status, and it is one of the oldest and most popular games in the world.
The origin of chess is a subject of dispute. The most common theory is that the game of chess originated from a game called Chaturanga in Punjab, India at some time in the 6th century AD. Other theories say its origin is the game of xiangqi in China, where opponents played the game with dice. It is widely agreed that chess originated in the far East. The game eventually spread via invasions or trade routes around Asia; first to Egypt in the 7th century AD, and then Persia. In the 8th century, it reached Europe, where Charlemagne first played it at the turn of the 9th century, the same period that it reached Russia. The spread of chess also faced opposition, as it was banned for a time in Japan, Egypt, Russia, and some areas in the Byzantine Empire. The precursor to modern chess boards appeared in the 11th century when checkered boards came into existence. Board sizes also fluctuated over the centuries, from ten-by-eight grids to fourteen-by-ten grids, among other configurations. Until the late 19th century, chess was considered to be a game that only gentlemen played, but during the 20th century it became popular among the working class and women as well. The first tournaments that treated chess as a sport, began in the 19th century, as did chess clubs in colleges. Computers began playing chess when Alan Turing wrote the first chess-playing program in 1950. Computerized players evolved quickly until Deep Blue, a chess-playing computer designed by IBM, defeated world chess Grandmaster Garry Kasparov in 1997.
There is a variety of organizations and groups around the world that pertain to the game of chess. The largest and one of the oldest is the World Chess Federation, also known as FIDE, which is based in Paris, France. There is also the International Braille Chess Association, which caters to blind people, and the International Correspondence Chess Federation, which pertains to chess games played by mail. The National Scholastic Chess Foundation is an organization that promotes the game of chess to young school children. The Chess Olympiad is an Olympics-style organization that hosts chess tournaments. There are also organizations that focus specifically on players in India, England, the United States, Japan, Russia, China, and other nations.
Chess is a two-player game, with one player controlling black pieces and the other controlling the white pieces. Each of the two players starts with 16 game pieces, and the one that controls the white pieces goes first. The pieces are arranged with two castle-shaped Rooks, each in the rear corner of the end row closest to the player, with a Bishop next to the Rook, a horse-shaped Knight next to each Bishop, and a Queen and a King in the center. This row is arranged behind a second row that has eight Pawns. Pawns are the weakest pieces on the board, being able to move directly forward by only one square. A Pawn may only move two squares forward on its first move. It may also move diagonally by one square to capture and remove a piece from play. The Rook can move horizontally on the board, which means that the Rook can move from left to right, or it can move up and down, but not diagonally. The Bishop can move diagonally. The strongest piece on the board is the Queen, which has the movement abilities of both the Rook and the Bishop. This means that it can move both diagonally and horizontally. The King is the most important piece, as it must avoid capture in order for the game to continue. A player whose King gets captured, loses the game. The Knight moves in an "L" formation, which means it moves either two squares forward and then one square sideways, or it may move two squares sideways and one square forward. No piece may move onto another square that is occupied by another piece that's the same color. If the piece is a different color, however, the piece on the targeted square may be captured. In some games, players are required to move any piece that they touch.
The game of chess has three phases, which are known as the opening, middlegame, and endgame. The opening phase is the name given to the first moves of the game. The goal of the opening phase is to position one's pieces in preparation for the middlegame, as well as gaining control of the center squares of the chess board. The middlegame is where most of the action occurs, including the capturing of other pieces. This is where control of the center of the board is translated into a numerical advantage in which the opponent's army is greatly reduced. Once this is done the game transitions into the endgame. The endgame either ends in checkmate, or a stalemate. A stalemate is when one player's King can no longer make a move that doesn't put it in check, which is the immediate danger of being captured.
With 16 pieces per player and a battlefield of 64 squares, chess offers a nearly unlimited choice of strategies and tactics to achieve victory. Popular tactical moves include forking, which put both the King and another important piece (such as the Queen or Rook) in immediate danger of capture (known officially as "in check"). Unlike tactics, strategies are long-term moves that involve in-depth planning. A popular example of a chess strategy is to get control of the central area on the board. This inhibits the opposition from making moves against the player and can allow the player to strike effectively at the opposition. Another important strategy is to maintain the initiative, which means to keep the opposing player on the defensive so that they are unable to execute their own plans for victory. Famous chess strategies and tactics include the Sicilian Defense, the Italian Game, and the Giuoco Piano.
Chess compositions are defined as puzzles that are designed using a chess board with chess pieces. The origin of chess compositions dates as far back as the 9th century in Baghdad. Caliph al-Mutasim Billah of Baghdad was known to have created chess problems based on game rules that differ from those of modern chess. A classic chess problem requires that the composed puzzle is achievable by a series of legal chess moves. Not all chess problems, however, follow this rule. For instance, there is the Eight Queens problem which requires the placement of eight queens on the board in a pattern which doesn't put one within striking range of another. Chess compositions are rated by difficulty, and their rating corresponds to the level of difficulty. Ratings range from a minimum of 500 up to a maximum of 3000. The FIDE, among other organizations, rate chess compositions. One famous chess problem is the Knight's Tour, a puzzle whose goal is to find a way for the Knight to visit each square exactly once.