Chess

Chess is a two-player strategy game of pure skill. It is regarded as one of the deepest and most complex games in existence. The number of legal positions in chess is estimated to be 10⁴³; the number of possible games is much larger and greatly exceeds the estimated number of particles in the observable universe. Chess is also the most popular board game in the western world. It is actively played in clubs, tournaments, on-line, and by mail.

Rules

Chess is played between two players on a 64-square chess board. Each player controls sixteen pieces: a king, a queen, two rooks, two bishops, two knights and eight pawns. The pieces are arranged as follows at the beginning of the game:

+---+---+---+---+---+---+---+---+
| r | n | b | q | k | b | n | r |
+---+---+---+---+---+---+---+---+
| p | p | p | p | p | p | p | p |
+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+
| P | P | P | P | P | P | P | P |
+---+---+---+---+---+---+---+---+
| R | N | B | Q | K | B | N | R |
+---+---+---+---+---+---+---+---+

By convention, diagrams display the starting position of the white pieces at the bottom of the board.

The player controlling the white pieces moves first, then the players alternate moves.

Check, Checkmate:

The object of the game is checkmate, a situation in which the opponent's king is threatened with capture and has no way out. A position in which the king is threatened with capture but has a way out is called check; a player can never move the king into check, and must always rescue the king from check immediately.

Draw:

The game ends drawn on one of these conditions:

The player to move is not in check and has no legal move (stalemate).
There is no possibility for either player to mate the opponent (for example, because there are insufficient pieces remaining).
By agreement of the players.

Either player may claim a draw by indicating that one of these conditions exists:

Fifty moves have been played by each player without a piece being taken or a pawn moved.
The same board position has been repeated three times, with the same player to move and all pieces having the same rights to move (castling and en passant, see below).

Tournament games are played under time constraints. If a player oversteps his alloted time, he loses automatically. Various tournament rules have been devised to prevent players from playing on in drawn positions, with no practical chances of winning on the board, intending merely to win when their opponent runs out of time. If a player believes his opponent is attempting to win a drawn position on time, he may appeal to a tournament official. The tournament official then either declares the game to be drawn, or penalizes the player who made the appeal and orders the game to continue.

Moving:

A move is

Moving a piece to an empty square.
Moving a piece to a square occupied by an opposing piece and removing the enemy piece (capture).
Castling (see below).
Promotion (see pawn below).
En passant (see pawn below).

The rook moves in a straight line horizontally or vertically. The bishop moves in a straight line diagonally. Neither may move through or 'jump over' a square occupied by another piece.

+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   |   | * |   |   |   |   |            |   |   |   | * |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   |   | * |   |   |   |   |            | * |   | * |   |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   |   | * |   |   |   |   |            |   | B |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
| * | * | * | R | * | * | * | * |            | * |   | * |   |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   |   | * |   |   |   |   |            |   |   |   | * |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   |   | * |   |   |   |   |            |   |   |   |   | * |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   |   | * |   |   |   |   |            |   |   |   |   |   | * |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   |   | * |   |   |   |   |            |   |   |   |   |   |   | * |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+

A queen moves in a straight line in any of eight directions, thus combining the power of the rook and the bishop. This makes the queen the most powerful piece.

A knight moves by 'jumping' in an L-shaped pattern, two squares vertically and one horizontally, or two squares horizontally and one vertically. The knight is the only piece that may jump over other pieces to reach its destination.

+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
| * |   |   | * |   |   | * |   |            |   |   |   |   |   | R | n | r |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   | * |   | * |   | * |   |   |            |   |   |   |   | ° | B | p | p |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   | * | * | * |   |   |   |            |   |   |   |   |   | ° |   | ° |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
| * | * | * | Q | * | * | * | * |            | * |   | * |   |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   | * | * | * |   |   |   |            |   |   |   | * |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   | * |   | * |   | * |   |   |            |   | N |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
| * |   |   | * |   |   | * |   |            |   |   |   | * |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   |   | * |   |   |   | * |            | * |   | * |   |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+

A king moves to any adjacent square, either diagonally, vertically or horizontally. The king must not be left in check, nor may he move to a square where he could be taken.

A pawn moves straight forward by one square. A pawn in its starting position has the option to move forward two squares. A pawn captures diagonally forward, making it the only piece which captures differently than it moves. If a pawn reaches the 8th rank, it must immeidately be promoted, i.e. replaced with a knight, rook, bishop, or queen of its own color.

+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   |   |   |   | ° | ° |   |            |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   |   |   | ° | k | ° |   |            |   | n |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   | B |   | ° | ° |   |   |            |   | P |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |            |   |   |   | * |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   | * | * | * |   |   |   | N |            | * |   |   | P |   |*r | b |*n |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   | * | K | * |   |   |   |   |            | * |   |   |   |   |   | P |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   | * | * | * |   |   |   |   |            | P |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |            |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+            +---+---+---+---+---+---+---+---+

A pawn moving two squares can be captured by an opposing pawn that could have captured it if it had only moved on square. This may only be done on the next move. Thus a black pawn on the fourth rank can capture a white pawn making its initial (two-step) move on a square directly beside the black pawn. Similarly, a white pawn on the fifth rank can capture a black pawn making the corresponding move. This en passant move was added soon after the two-space initial pawn move to preserve the interaction of pawns.

Castling involves moving the king two spaces toward a rook of the same color and moving the rook to the space immediately beyond the king. It protects the king and brings out the rook for action. A player can only castle if all of the conditions are met:

Neither the king nor the rook has moved
There are no pieces between the king and rook
The king is not moving into, out of, or through check.

|   |   |   |   |   |   |   |   |       |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+  __   +---+---+---+---+---+---+---+---+
| R |   |   |   | K | B |   | R |    /  |   |   | K | R |   | B |   | R |
+---+---+---+---+---+---+---+---+       +---+---+---+---+---+---+---+---+
Queen-side castling

|   |   |   |   |   |   |   |   |       |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+  __   +---+---+---+---+---+---+---+---+
| R |   | B | Q | K |   |   | R |    /  | R |   | B | Q |   | R | K |   |
+---+---+---+---+---+---+---+---+       +---+---+---+---+---+---+---+---+
King-side castling

In tournament play and for quick chess, a chess clock is used; each player presses a button after every move and the clock keeps track of the time remaining for each player. If a player runs out of time before the game is decided in some other way, that player loses the game. In correspondence chess, the moves are sent by mail and every player is given a set number of days per move.

Strategy and Tactics

Some rules of thumb for playing well are given in the Chess Strategy and Tactics article.

The world of Chess

Lists of World Champions and famous players are available.

The world organization of chess players is the FIDE which organizes regular world chess championships. In recent years, some players complained about arbitrary decisions by FIDE and left to start competing organizations.

Strong players are awarded the lifetime titles "International Master" and "Grandmaster" by FIDE according to well-defined rules.

History

Chess originated from the Indian game Shatranj, about 1400 years ago. This game is related to xiang4 qi2 (象棋 Chinese Chess) in China, and Shogi in Japan. The game reached Russia via Mongolia, where it was played at the beginning of the 7th century. From India it migrated to Persia, and spread throughout the Islamic world after the muslim conquest of Persia. It was introduced into Spain by the Moors in the 10th century, where a famous games manuscript covering chess, backgammon, and dice, named the Libros de las Juegos, was written under the sponsorship of Alphonso X of Spain during the 13th century. Chess reached England in the 11th century, and evolved through various versions such as Courier.

By the end of the 15th century, the modern rules were adopted: pawns could move two squares on their first move, bishops could move diagonally arbitrary far (before, they jumped three squares diagonally) and the queen was allowed to move arbitrary far in every direction (before, she could only move one square diagonally). The game in Europe since that time has been almost the same as is played today. The current rules were completely finalized in the early 19th century.

The most popular piece design, the "Staunton set", was created by Nathaniel Cook in 1849, endorsed by the then leading player Howard Staunton, and officially adopted by FIDE in 1924.

The title "Grandmaster" was created by Russian Tsar Nicholas II who first awarded it after a tournament in Saint Petersburg which he had funded.

Famous people who were avid chess players

Computer chess

Chess enthusiasts and computer engineers have attempted to build, with increasing degrees of seriousness and success, chess-playing machines for over a century. Their motivations can essentially be consolidated into two: firstly, to build a machine to play chess with for solo entertainment, and secondly, to investigate chess as a problem which might provide some insight into human cognition. In this view, the history of computer chess is both a spectactular success and a virtually complete failure. Chess-playing computers are available for negligible cost, and even the free gnuchess software plays a game that, with the aid of virtually any modern personal computer can defeat most master players under tournament conditions. However, to the surprise and disappointment of many, chess has taught us little about building machines that offer human-like intelligence, or indeed do anything except play excellent chess.

fill in early history etc.*

In May 1997, a computer (IBM's updated Deep Blue) defeated the then reigning world champion Gary Kasparov in a match. IBM keeps a web site of the event at http://www.chess.ibm.com. While not an official world championship, the outcome of the match is often taken to mean that the strongest player in the world is a computer. Such a claim is open to strong debate. Firstly, there are other players whose playing style is recognised as more effective against other computer opponents. Secondly, it was impossible for Kasparov to prepare to play the machine as he would against a human opponent, as the computer's programming was adjusted between prior matches and the Kasparov match. If the machine's programming had been left fixed, it would have been easier for Kasparov to figure out and play against the weaknesses of the machine. Thus, a truly fair match is very difficult to arrange. IBM retired Deep Blue after the match and it has not played since. However, given that computer hardware and chess algorithms have continued to improve since 1997 it seems likely that an equivalent effort would produce a computer that was more unambiguously stronger than the best human player.

It should be noted that computer chess is not of great academic interest to researchers in artificial intelligence. Chess-playing programs essentially explore huge numbers of potential future moves by both players and apply a relatively simple evaluation function to the positions that result. Such methods are useless for most other problems artificial intelligence researchers have tackled, and are believed to be very different from how human chess players select their moves. In some strategy games, computers easily win every game, while in others they are regularly beaten even by amateurs. Therefore, the fact that the best efforts of chess masters and computer engineers are so finely balanced should probably be viewed as an amusing quirk of fate rather than the profound comment on thought that many in the past, including some of the early theorists on machine intelligence, thought it to be.

Composition chess

needs to be filled in

Variants

There are many variants of chess. A few of these include:

suicide, giveaway, or losers where capturing moves are mandatory and the object is to lose all pieces,
Fischer Random where the placement of the pieces on the 1st and 8th rank is randomized to disemphasize the value of opening theory,
bughouse, tandem or Siamese where two teams of two players face each other on two boards, the team players play different colors and the pieces captured by one partner can be placed on the board by the other instead of moving,
advanced chess where the players are allowed to consult a computer, and
Kriegspiel where each player does not know where the opponent's pieces are but can deduce them with information from a referee.

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