Castling

Castling counts as one move but moves two pieces. The king travels two squares toward a rook, and that rook moves to the square the king just crossed.

Short and long castling

• In kingside castling, also called short castling, White's king moves from e1 to g1 and the rook from h1 to f1.
• In queenside castling, also called long castling, White's king moves from e1 to c1 and the rook from a1 to d1.
• Black makes the equivalent moves on the eighth row.

Castling usually takes the king away from the center, where attacks may open, and brings a rook closer to the center. One move can therefore improve king safety and rook activity.

When castling is legal

• The king has not moved earlier.
• The chosen rook has not moved earlier.
• No piece stands between the king and that rook.
• The king is not in check, and its starting, crossing, and destination squares are not attacked by an enemy piece. Check means that the king is attacked and must be made safe.

The king cannot travel through danger. The rook, however, may be under attack, and a square crossed only by the rook may also be attacked.