Game Rules
Setup
Pieces at the start of a game and a chess clock.
Initial position. First row: rook, knight, bishop, queen, king, bishop,
knight, and rook. Second row: pawns.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 colors are
chosen either by a friendly agreement, by a game of chance or by a
tournament director. 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.
Moves
Each chess piece has its own style of moving. The X's mark the squares where the piece can move if no other pieces are on the X's between the piece's initial position and destination. If there is an opponent's piece at the destination square, then moving piece can capture the opponent's piece. The only exception is the pawn which can only capture the white circles.
Special Moves
Castling
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, described later).
En passant
When a pawn advances two squares, if there is an opponent's pawn on an
adjacent file next to its destination square, then the opponent's pawn
can capture it and move to square the pawn passed over, but only on the
next move. For example, if the black pawn on g5 has just advanced two
squares to g5, then one of the white pawns can take it via en passant on
g6.
Promotion
When a pawn advances to its eighth rank, it is exchanged for the
player's choice of a queen, rook, bishop, or knight of the same color.
Usually, the pawn is chosen to be promoted to a queen, but in some cases
another piece is chosen, called underpromotion. In the diagram on the
right, the pawn on c7 can choose to advance to the eighth rank to
promote to a better piece.
Game's end
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).
Time control
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, the game is automatically
lost. 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).
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 maneuver. These two parts 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 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 the 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. In the endgame, the king is generally more powerful than a minor
piece but less powerful than a rook, thus it is sometimes assigned a
fighting value of 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 of a bishop and 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 puzzle 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
Encyclopaedia 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.[8] Professional players spend years studying openings, and
continue doing so throughout their careers, as opening theory continues
to evolve.
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 (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.
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 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".