Castling is a move in chess. It consists of moving the king two squares toward a rook on the same and then moving the rook to the square that the king passed over. Castling is permitted only if neither the king nor the rook has previously moved; the squares between the king and the rook are vacant; and the king does not leave, cross over, or finish on a square attacked by an enemy piece. Castling is the only move in chess in which two pieces are moved at once. Castling with the is called castling , and castling with the is called castling . In both algebraic and descriptive notation, castling kingside is written as 0-0 and castling queenside as 0-0-0. Castling originates from the king's leap, a two-square king move added to European chess between the 14th and 15th centuries, and took on its present form in the 17th century; however, local variations in castling rules were common, persisting in Italy until the late 19th century. Castling does not exist in Asian games of the chess family, such as shogi, xiangqi, and janggi, but it commonly appears in variants of Western chess. Rules Description During castling, the king is shifted two squares toward a rook of the same color on the same rank, and the rook is transferred to the square crossed by the king. There are two forms of castling: Castling kingside (short castling) consists of moving the king to g1 and the rook to f1 for White, or moving the king to g8 and the rook to f8 for Black. Castling queenside (long castling) consists of moving the king to c1 and the rook to d1 for White, or moving the king to c8 and the rook to d8 for Black. Requirements Castling is permitted provided all of the following conditions are met: Neither the king nor the rook has previously moved. There are no pieces between the king and the rook. The king is not currently in check. The king does not pass through or finish on a square that is attacked by an enemy piece. Conditions 3 and 4 can be summarized by the mnemonic: A player may not castle out of, through, or into check. Castling rules often cause confusion, even occasionally among high-level players. To clarify: The rook can be under attack. The rook can pass through an attacked square. (White can