3.1. No piece can be moved to a square occupied by a piece of the same colour. If a piece moves to a square occupied by an opponent's piece the latter is captured and removed from the chessboard as part of the same move. A piece is said to attack a square if the piece could make a capture on that square according to Articles 3.2 to 3.5.

 

3.2. (a) The queen moves to any square along the file, the rank or a diagonal on which it stands.

(b) The rook moves to any square along the file or the rank on which it stands.

(c) The bishop moves to any square along a diagonal on which it stands.

 

When making these moves the queen, rook or bishop cannot move over any intervening pieces

.

3.3. The knight moves to one of the squares nearest to that on which it stands but not on the same rank, file or diagonal. It does not pass directly over any intervening square.

 

3.4. (a) The pawn moves forward to the unoccupied square immediately in front of it on the same file, or

(b) on its first move the pawn may advance two squares along the same file provided both squares are unoccupied, or

(c) the pawn moves to a square occupied by an opponent's piece which is diagonally in front of it on an adjacent file, capturing that piece.

(d) A pawn attacking a square crossed by an opponent's pawn which has advanced two squares in one move from its original square may capture this opponent's pawn as though the latter had been moved only one square. This capture can be made only on the move following this advance and is called an 'en passant' capture.

(e) When a pawn reaches the rank furthest from its starting position it must be exchanged as part of the same move for a queen, rook, bishop or knight of the same colour. The player's choice is not restricted to pieces that have been captured previously. This exchange of a pawn for another piece is called 'promotion' and the effect of the new piece is immediate.

 

3.5. (a)The king can move in two different ways, by:

(i) moving to any adjoining square that is not attacked by one or more of the opponent's pieces,

or

(ii) 'castling'. This is a move of the king and either rook of the same colour on the same rank, counting as a single move of the king and executed as follows: the king is transferred from its original square two squares towards the rook, then that rook is transferred over the king to the square the king has just crossed.

(1) Castling is illegal:

[a] if the king has already been moved, or

[b] with a rook that has already been moved

(2) Castling is prevented for the time being:

[a] if the square on which the king stands, or the square which it must cross, or the square which it is to occupy, is attacked by one or more of the opponent's pieces.

[b] if there is any piece between the king and the rook with which castling is to be effected.

(b) The king is said to be 'in check', if it is under attack by one or more of the opponent's pieces, even if such pieces cannot themselves move.

Declaring a check is not obligatory.

A player must not make a move which places or leaves his own king in check.