Chess

Chess is a two-player strategy game of pure skill. and probably one of the deepest and most complex games commonly played in Western cultures (the game of go holds a similar place in Asian cultures). It is nonetheless also the most popular board game in the West, played both recreationally and competitively in clubs, tournaments, on-line, and by mail.

It is played on a square board divided into 64 smaller squares on which move 16 "white" and 16 "black" pieces controlled by the two players. Sets used for play are commonly made of wood or plastic, though "ornamental" sets of stone, glass, or metal are often used to decorate homes.

A typical Staunton-design set and clock

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.

History

Chess originated from the Indian game Shatranj, about 1400 years ago. The 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 gained the option to move two squares on their first move, bishops could move diagonally arbitrarily far (before, they moved exactly two squares diagonally, jumping over the intervening square), the queen was allowed to move arbitrarily far in every direction. making it the most powerful piece (before, she could only move one square diagonally).

These changes collectively helped popularize chess by making the action faster-paced. 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.

Rules

File:Cb start.png

Chess is played between two players on a 64-square chessboard, with squares of alternating light and dark colors. The board is placed so that a light-colored square is in the corner nearest each player's right hand. Each player controls sixteen pieces: a king, a queen, two rooks, two bishops, two knights and eight pawns. The pieces are arranged as shown in the diagram to the left at the beginning of the game.

The player controlling the white pieces moves first, then the players alternate moves. A "move" is any one of:

Moving a single piece of your own color from the square it is currently on to an empty square, according to that piece's method of movement;
Moving a piece to a square occupied by an opposing piece and removing the enemy piece (called a capture);
Castling (see castling);
Promotion (see pawn); or
En passant capture (see pawn).

For the moving methods of the individual pieces, see king, queen, rook, bishop, kinght, and pawn.

Check, Checkmate

A player's king is never captured. When a player makes a move that threatens the opposing king with capture, the king is said to be in check, and the player with the move is required to immediately eliminate the threat by one of three means:

Move the king to a square not threatened;
Capture the threatening piece; or
Interpose a piece between the king and the threatening piece.

A player may never leave his king in check at the end of his move.

In informal games, it is customary to announce "check" when making a move that puts the opponent's king in check. In formal competitions, this is not only unnecessary but may be considered annoying or distracting.

If a player's king is placed in check, and there is no legal move that player can make to escape check, then the king is said to be checkmated, the game ends, and that player loses. The diagram to the right shows a typical checkmate position. The white king is under attack by the black queen; every square to which the king could move is also attacked; and he cannot capture the queen, because he would then be attacked by the rook.

File:Cb checkmate.png

Draws

File:Cb stalemate.png

The game ends in a draw on one of these conditions:

The player to move is not in check but has no legal move (this is called a stalemate, and such a position is shown in the diagram to the left);
There is no possibility for either player to mate the opponent, 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 captured 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 (including such things as the right to castle or capture en passant).

Tournament games are played under time constraints. If a player oversteps his allotted 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.

Games of chess are frequently recorded as they are played for later analysis. Algebraic chess notation is presently used for this, though some older books still use English chess notation.

Strategy and Tactics

Some rules of thumb for playing well are given in the Chess strategy and tactics article. A Sample_chess_game gives examples of how pieces move and capture, as well as an introdution to the thought processes of chess players.

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.

Famous people who were avid chess players

Catherine the Great

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 a piece captured by one partner may be placed on the board by the other in lieu of a move,
baroque chess where the pieces all move like queens but have various capturing methods,
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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