Monday, May 19, 2008


Chess is a recreational and competitive game played between 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 during the second half of the 15th century after evolving from similar, much older games of Indian and Persian origin. Today, chess is one of the world's most popular games, played by millions of people worldwide in clubs, online, by correspondence, in tournaments and informally.

The game is played on a square chequered chessboard with 64 squares arranged in an eight-by-eight square. At the start, each player (one controlling the white pieces, the other controlling the black pieces) 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.

The tradition of organized competitive chess started in the sixteenth century and has developed extensively. Chess today is a recognized sport of the International Olympic Committee. The first official World Chess Champion, Wilhelm Steinitz, claimed his title in 1886; Viswanathan Anand is the current World Champion. Theoreticians have developed extensive chess strategies and tactics since the game's inception. Aspects of art are found in chess composition.

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 and by the possibility to play online. In 1996, a match between Garry Kasparov, then World Champion, and a computer proved for the first time that machines are able to beat even the strongest human players.

Chess is played on a square board of eight rows (called ranks and denoted with numbers 1 to 8) and eight columns (called files and denoted with letters a to h) of squares. The colors of the sixty-four squares alternate and are referred to as "light squares" and "dark squares". The chessboard is placed with the light squares at the players' right, and the pieces are set out as shown in the diagram, with each queen on its own color.

The pieces are divided, by convention, into White and Black sets. Each player is referred to by the color of their pieces and begins the game with sixteen pieces. These comprise one king, one queen, two rooks, two bishops, two knights and eight pawns. White moves first. The players alternate moving one piece at a time (with the exception of castling, when two pieces 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 king is under immediate attack by the opponent's pieces, the king is said to be in check. When in check, only moves that result in a position in which the king is not in check are permitted. Each player must not make any move that would place their king in check. The object of the game is to checkmate the opponent; this occurs when the opponent's king is in check, and there is no way to remove the king from attack.

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 puzzle aimed at development of players' skills.

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 Defence. They are catalogued in reference works such as the Encyclopaedia of Chess Openings.

There are dozens of different openings, varying widely in character from quiet positional play (e.g. the RĂ©ti 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.

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.

Most players and theoreticians consider that White, by virtue of the first move, begins the game with a small advantage. Black usually strives to neutralize White's advantage and achieve equality, or to develop dynamic counterplay in an unbalanced position.

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 (i.e. simplify). 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.

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 endgame:

* 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 brought to the center of the board where it can protect its own pawns, attack the pawns of opposite color, and hinder movement of the opponent's king.
* 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. For example, in the diagram on the right, Black on move must go 1...Kb7 and allow white to queen after 2.Kd7, while White on move must allow a draw either after 1.Kc6 stalemate or losing the last pawn by going anywhere else.

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. For example, 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 endgame".

No comments: