# Castling

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Castling is a special move in the game of chess involving the king and either of the original rooks of the same color. It is the only move in chess (leaving aside promotion) in which a player moves two pieces at the same time. Castling consists of moving the king two squares towards a rook on the player's first rank, then moving the rook onto the square over which the king crossed.[1] Castling can only be done if the king has never moved, the rook involved has never moved, the squares between the king and the rook involved are not occupied, the king is not in check, and the king does not cross over or end on a square in which it would be in check. Castling is one of the rules of chess and is considered a king move (Hooper & Whyld 1992).

The notation for castling, in both the descriptive and the algebraic systems, is 0-0 with the kingside rook and 0-0-0 with the queenside rook. In PGN, O-O and O-O-O are used instead. Castling on the kingside is sometimes called castling short and castling on the queenside is called castling long; the difference being based on whether the rook moves a short distance (two squares) or a long distance (three squares) (Hooper & Whyld 1992).

Castling is in most European languages other than English known as 'rochieren/rochada/roque/arrocco' or some other derivative of the same root (from which also the English word 'rook' is derived), while the local adjectives meaning 'long' and 'short' are used in those countries to refer to 'queenside/kingside castling'. Castling was added to European chess in the 14th or 15th century and did not develop into its present form until the 17th century. The Asian versions of chess do not have such a move.

## Contents

### Requirements

Castling is permissible if and only if all of the following conditions hold: (Schiller 2001:19)

Rules 4 through 6 may be summarized with the more memorable phrase "One cannot castle out of, through, or into check."