Chess

Chess is a recreational and competitive game for two players. Sometimes called Western Chess or International Chess to distinguish it from its predecessors and other chess variants, the current form of the game emerged in Southern Europe in the second half of the 15th century after evolving from similar, much older games of Indian origin.

Today, chess is one of the world's most popular games, played by an estimated 605 million people worldwide in clubs, offline, by correspondence (mail and e-mail), in tournaments (amateur and professional) and informally. Aspects of art and science are found in chess composition and theory. Chess is also advocated as a way of enhancing mental prowess.

The game is played on a square chequered chessboard. At the start, each player ("white" and "black") controls sixteen pieces: one king, one queen, two rooks, two knights, two bishops, and eight pawns. The object of the game is to checkmate the opponent's king, whereby the king is under immediate attack (in "check") and there is no way to remove it from attack on the next move. Theoreticians have developed extensive chess strategies and tactics since the game's inception.

The tradition of organized competitive chess began in the 16th century. The first official World Chess Champion, Wilhelm Steinitz, claimed his title in 1886; Vladimir Kramnik, today, is the 14th Champion in this lineage. There are also biennial world team events called Chess Olympiads. Since the 20th century, two international organizations, the World Chess Federation and the International Correspondence Chess Federation have organized and overseen the top chess competitions and international titles.

One of the goals of early computer scientists was to create a chess-playing machine, and today's chess is deeply influenced by the abilities of current chess programs. In 1997, a match between Garry Kasparov, then World Champion, and IBM's Deep Blue chess program proved for the first time that computers are able to beat even the strongest human players. The popularity of online chess coincided with the growth of the Internet, which started in the mid 1990s.

Rules

For a simple demonstration of the gameplay, see sample chess game. Chess is played on a square board of eight rows (called ranks and numbered 1 to 8) and eight columns (called files and labeled a to h) of squares. The colors of the sixty-four squares alternate and are referred to as "light squares" and "dark squares". The pieces are divided into two matching sets, by convention called White and Black. Each player, referred to by the color of his pieces, begins the game with sixteen pieces: these comprise one king, one queen, two rooks, two bishops, two knights and eight pawns.

The colors are chosen either by a friendly agreement, by a game of chance or by a tournament director. The chessboard is placed with a light square at each player's right on the nearest rank, and the pieces are set out on the first and last two ranks as shown in the diagram. Each queen stands on a square of its own color.

White makes the first move. The players then alternate moving one piece of their own at a time (with the exception of castling, when a rook and the king are moved simultaneously). Pieces are moved to either an unoccupied square, or one occupied by an opponent's piece, capturing it and removing it from play. With one exception (en passant), all pieces capture opponent's pieces by moving to the square that the opponent's piece occupies. When a piece can be captured on the opposing player's next move, it is said to be "threatened" or "under attack".

When a player's king is under direct attack, it is said to be in check. A player is not permitted to make any move that would place her king in check, and if her king is put in check she is then required to immediately make a move that takes the king out of check. If no such move is available, the player is checkmated. The object of the game is to checkmate the opponent.

Each chess piece has its own style of moving.

The king can move only one square horizontally, vertically, or diagonally. Once in every game, each king is allowed to make a special move, known as castling. Castling consists of moving the king two squares towards a rook, then placing the rook immediately on the far side of the king. Castling is only permissible if all of the following conditions hold:

The player must never have moved either the king or the rook involved in castling;
There must be no pieces between the king and the rook;
The king may not currently be in check, nor may the king pass through squares that are under attack by enemy pieces. As with any move, castling is illegal if it would place the king in check.
The king and the rook must be on the same rank (to exclude castling with a promoted pawn).

The rook moves any number of vacant squares vertically or horizontally (it is also involved in the king's special move of castling);
The bishop moves any number of vacant squares in any direction diagonally. Note that a bishop never changes square color, therefore players speak about "dark-squared" or "light-squared" bishops, depending on the color of square on which the bishop resides. Alternatively, bishops may be identified as a "queen bishop" or a "king bishop", depending on whether they are next to the queen or the king when on their home square.
The queen can move any number of vacant squares diagonally, horizontally, or vertically;
The knight can jump over occupied squares and moves two spaces horizontally and one space vertically or vice versa, making an "L" shape. A knight in the middle of the board has eight squares to which it can move. Note that every time a knight moves, it changes square color.
Pawns have the most complex rules of movement:

A pawn can move forward one square, if that square is unoccupied. If it has not yet moved, the pawn has the option of moving two squares forward, if both squares in front of the pawn are unoccupied. A pawn cannot move backward.
When such an initial two square advance is made that puts that pawn horizontally adjacent to an opponent's pawn, the opponent's pawn can capture that pawn "en passant" as if it moved forward only one square rather than two, but only on the immediately subsequent move.
Pawns are the only pieces that capture differently than they move. They can capture an enemy piece on either of the two spaces adjacent to the space in front of them (i.e., the two squares diagonally in front of them), but cannot move to these spaces if they are vacant.
If a pawn advances all the way to its eighth rank, it is then promoted (converted) to a queen, rook, bishop, or knight of the same color. In practice, the pawn is almost always promoted to a queen.

With the exception of the knight, pieces cannot jump over each other. One's own pieces ("friendly pieces") cannot be passed if they are in the line of movement, and a friendly piece can never replace another friendly piece. Enemy pieces cannot be passed, but they can be "captured". When a piece is captured (or taken), the attacking piece replaces the enemy piece on its square (en passant being the only exception). The captured piece is thus removed from the game and may not be returned to play for the remainder of the game.The king cannot be captured, only put in check. If a player is unable to get the king out of check, checkmate results, with the loss of the game.

Chess games do not have to end in checkmate — either player may resign if the situation looks hopeless. Games also may end in a draw (tie). A draw can occur in several situations, including draw by agreement, stalemate, threefold repetition of a position, the fifty move rule, or a draw by impossibility of checkmate (usually because of insufficient material to checkmate).

Besides casual games without exact timing, chess is also played with a time control, mostly by club and professional players. If a player's time runs out before the game is completed, he automatically loses. The timing ranges from long games played up to seven hours to shorter rapid chess games lasting usually 30 minutes or one hour per game. Even shorter is blitz chess with a time control of three to fifteen minutes for each player and bullet chess (under three minutes).

The international rules of chess are described in more detail in the FIDE Handbook, section Laws of Chess.

Strategy and tactics

Chess strategy consists of setting and achieving long-term goals during the game — for example, where to place different pieces — while tactics concentrate on immediate maneuvers. These two sides of chess thinking cannot be completely separated, because strategic goals are mostly achieved by the means of tactics, while the tactical opportunities are based on the previous sound strategy of play.

Because of different strategic and tactical patterns, a game of chess is usually divided into three distinct phases: Opening, usually the first 10 to 25 moves, when players develop their armies and set up the stage for the coming battle; middlegame, the developed phase of the game; and endgame, when most of pieces are gone and kings start to take an active part in the struggle.

Fundamentals of strategy

Chess strategy is concerned with evaluation of chess positions and with setting up goals and long-term plans for the future play. During the evaluation, players must take into account the value of pieces on board, pawn structure, king safety, space, and control of key squares and groups of squares (for example, diagonals, open-files, and dark or light squares).

The most basic, is to count the total value of pieces of both sides. The point values used for this purpose are based on experience; usually pawns are considered worth one point, knights and bishops about three points each, rooks about five points (the value difference between a rook and a bishop being known as the exchange), and queens about nine points. The fighting value of the king in the endgame is equivalent to about four points. These basic values are then modified by other factors like position of the piece (for example, advanced pawns are usually more valuable than those on initial positions), coordination between pieces (for example, a pair of bishops usually coordinates better than the pair bishop + knight), or type of position (knights are generally better in closed positions with many pawns while bishops are more powerful in open positions).

Another important factor in the evaluation of chess positions is the pawn structure (sometimes known as the pawn skeleton), or the configuration of pawns on the chessboard. Pawns being the least mobile of the chess pieces, the pawn structure is relatively static, and largely determines the strategic nature of the position. Weaknesses in the pawn structure, such as isolated, doubled or backward pawns and holes, once created, are usually permanent. Care must therefore be taken to avoid them unless they are compensated by another valuable asset (for example, by the possibility to develop an attack).

Fundamentals of tactics

In chess, tactics in general concentrate on short-term actions — so short-term that they can be calculated in advance by a human player or by a computer. The possible depth of calculation depends on the player's ability or speed of the processor. In quiet positions with many possibilities on both sides, a deep calculation is not possible, while in "tactical" positions with a limited number of forced variants, it is possible to calculate very long sequences of moves.

Simple one-move or two-move tactical actions — threats, exchanges of material, double attacks etc. — can be combined into more complicated variants, tactical maneuvers, often forced from one side or from both. Theoreticians described many elementary tactical methods and typical maneuvers, for example pins, forks, skewers, discovered attacks (especially discovered checks), zwischenzugs, deflections, decoys, sacrifices, underminings, overloadings and interferences.

A forced variant which is connected with a sacrifice and usually results in a tangible gain is named a combination. Brilliant combinations — such as those in the Immortal game — are described as beautiful and are admired by chess lovers. Finding a combination is also a common type of chess pule aimed at development of players' skills.

Opening

A chess opening is the group of initial moves of a game (the "opening moves"). Recognized sequences of opening moves are referred to as openings and have been given names such as the Ruy Lopez or Sicilian Defense. They are catalogued in reference works such as the 'Encyclopedia of Chess Openings.

There are dozens of different openings, varying widely in character from quiet positional play (e.g. the Réti Opening) to very aggressive (e.g. the Latvian Gambit). In some opening lines, the exact sequence considered best for both sides has been worked out to 30-35 moves or more. Professional players spend years studying openings, and continue doing so throughout their careers, as opening theory continues to evolve. Uncovering one or two novelties in opening theory can be key to success in a high level match or tournament.

The fundamental strategic aims of most openings are similar:

Development: To place (develop) the pieces (particularly bishops and knights) on useful squares where they will have an impact on the game.
Control of the center: Control of the central squares allows pieces to be moved to any part of the board relatively easily, and can also have a cramping effect on the opponent.
King safety: It is often enhanced by castling.
Pawn structure: Players strive to avoid the creation of pawn weaknesses such as isolated, doubled or backward pawns, and pawn islands.

Apart from these fundamentals, other strategic plans or tactical sequences may be employed in the opening.

Middlegame

The middlegame is the part of the game when most pieces have been developed. Because the opening theory has ended, players have to assess the position, to form plans based on the features of the positions, and at the same time to take into account the tactical possibilities in the position.

Typical plans or strategical themes — for example the minority attack, that is the attack of queenside pawns against an opponent who has more pawns on the queenside — are often appropriate just for some pawn structures, resulting from a specific group of openings. The study of openings should therefore be connected with the preparation of plans typical for resulting middlegames.

Middlegame is also the phase in which most combinations occur. Middlegame combinations are often connected with the attack against the opponent's king; some typical patterns have their own names, for example the Boden's Mate or the Lasker—Bauer combination.

Another important strategical question in the middlegame is whether and how to reduce material and transform into an endgame. For example, minor material advantages can generally be transformed into victory only in an endgame, and therefore the stronger side must choose an appropriate way to achieve an ending. Not every reduction of material is good for this purpose; for example, if one side keeps a light-squared bishop and the opponent has a dark-squared one, the transformation into a bishops and pawns ending is usually advantageous for the weaker side only, because an endgame with bishops on opposite colors is likely to be a draw, even with an advantage of one or two pawns.

Endgame

The endgame (or end game or ending) is the stage of the game when there are few pieces left on the board. There are three main strategic differences between earlier stages of the game and

During the endgame, pawns become more important; endgames often revolve around attempting to promote a pawn by advancing it to the eighth rank.
The king, which has to be protected in the middlegame owing to the threat of checkmate, becomes a strong piece in the endgame and it is often advisable to bring it to the center of the board where it can protect its own pawns and attack the pawns of opposite color.
Zugzwang, a disadvantage because the player has to make a move, is often a factor in endgames and rarely in other stages of the game.

Endgames can be classified according to the type of pieces that remain on board. Basic checkmates are positions in which one side has only a king and the other side has one or two pieces and can checkmate the opposing king, with the pieces working together with their king. King and pawn endgames involve only kings and pawns on one or both sides and the task of the stronger side is to promote one of the pawns. Other more complicated endings are classified according to the pieces on board other than kings, e.g. "rook and pawn versus rook".y

Competitive play

Organization of competitions

Contemporary chess is an organized sport with structured international and national leagues, tournaments and congresses. Chess's international governing body is FIDE (Fédération Internationale des Échecs). Most countries have a national chess organization as well (such as the US Chess Federation and English Chess Federation), which in turn is a member of FIDE. FIDE is a member of the International Olympic Committee (IOC), but the game of chess has never been part of the Olympic Games; chess does have its own Olympiad, held every two years as a team event. An estimated 605 million people worldwide know how to play chess, and 7.5 million are members of national chess federations, which exist in 160 countries worldwide. This makes chess one of the most popular sports worldwide.

The current World Chess Champion is Vladimir Kramnik, and the reigning Women's World Champion is Xu Yuhua from China. However, the world's highest rated female player, Judit Polgar, has never participated in the Women's World Chess Championship, instead preferring to compete with the leading men.

Other competitions for individuals include the World Junior Chess Championship, the European Individual Championship and the National Chess Championships. Other elite tournaments include Spain's Linares event, Monte Carlo's Melody Amber tournament, the Dortmund Sparkassen meeting and Wijk aan Zee's Corus tournament.

Regular team chess events include the aforementioned Chess Olympiad and the European Team Championship. The 37th Chess Olympiad was held 2006 in Turin, Italy; Armenia won the gold in the unrestricted event, and Ukraine took the top medal for the women. The World Chess Solving Championship and World Correspondence Chess Championships are both team and individual events.

Besides these prestigious competitions, there are thousands of other chess tournaments, matches and festivals held around the world every year, which cater to players of all levels, from beginners to experts.

Titles and rankings

The best players can be awarded specific lifetime titles by the world chess organization FIDE:

International Grandmaster (shortened: Grandmaster, GM or IGM) is awarded to world-class chess masters. Apart from World Champion, Grandmaster is the highest title a chess player can attain. Before FIDE will confer the title on a player, the player must have an ELO chess rating (see below) of at least 2500 at one time and two favorable results (called norms) in tournaments involving other Grandmasters, including some from countries other than the applicant's. There are also other milestones a player can achieve to attain the title, such as winning the World Junior Championship.
International Master (shortened: IM). The conditions are similar to GM, but less demanding. The minimum rating for the IM title is 2400.
FIDE Master (shortened: FM). The usual way for a player to qualify for the FIDE Master title is by achieving a FIDE Rating of 2300 or more.
Candidate Master (shortened: CM). Similar to FM, but with a FIDE Rating of at least 2200.

All the titles are open to men and women. Separate women-only titles, such as Woman Grandmaster (WGM), are also available. In 1991, Susan Polgar became the first woman to earn the GM title under the same conditions as men, and most of the top ten women in 2006 hold the unrestricted GM title.y

International titles are awarded to composers and solvers of chess problems, and to correspondence chess players (by the International Correspondence Chess Federation). Moreover, national chess organizations may also award titles, usually to the advanced players still under the level needed for international titles; an example is the Chess expert title used in the USA.

In order to rank players, FIDE, ICCF and national chess organizations use the Elo rating system developed by Arpad Elo. Elo is a statistical system based on assumption that the chess performance of each player in his games is a random variable. Arpad Elo thought of a player's true skill as the average of that player's performance random variable, and showed how to estimate the average from results of player's games. The US Chess Federation implemented Elo's suggestions in 1960, and the system quickly gained recognition as being both fairer and more accurate than older systems; it was adopted by FIDE in 1970.

The highest ever FIDE rating was 2851, which Garry Kasparov had on the July 1999 and January 2000 lists.

Psychology

There is an extensive scientific literature on chess psychology. As early as 1894, Alfred Binet showed that knowledge, rather than ability to visualize positions, lies at the core of expertise. Adriaan de Groot, in his doctoral thesis, showed that chess masters can rapidly perceive the key features of a position. According to de Groot, this intuitive perception, made possible by years of practice and study, is more important than the sheer ability to anticipate moves. De Groot also showed that chess masters can memorize positions shown for a few seconds almost perfectly. Memorization ability alone does not account for this skill, since masters and novices, when faced with random arrangements of chess pieces, had equivalent recall (about half a dozen positions in each case). Rather, it is the ability to recognize patterns, which are then memorized, which distinguished the skilled players from the novices. When the positions of the pieces were taken from an actual game, the masters had almost total positional recall.

More recent research has focused on the respective roles of knowledge and look-ahead search; the role of practice and talent in the development of expertise; brain imaging studies of chess masters and novices; blindfold chess; the role of personality and intelligence in chess skill, gender differences, and computational models of chess expertise.