The three moves that surprise beginners.

Castling: two pieces, one move

Castling is the only move that moves two pieces at once. The king moves two squares toward a rook, and the rook jumps to the square the king crossed. Kingside castling is written O-O; queenside castling is O-O-O.

The conditions are strict. The king and the chosen rook must not have moved earlier in the game. The squares between them must be empty. The king may not be in check, pass through a square attacked by the enemy, or finish on an attacked square. The rook may be attacked; only the king’s path matters.

• Kingside: the king goes from e1 to g1; the rook goes from h1 to f1.
• Queenside: the king goes from e1 to c1; the rook goes from a1 to d1.
• Black castles on the same files from the eighth rank.
• You may not castle if the king or rook has already moved, even if it moved back.

En passant: one chance, immediately

En passant is a pawn capture that happens as if an enemy pawn had advanced only one square. It is available only when an enemy pawn moves two squares from its starting rank and lands beside your pawn on the same rank.

On your very next move, your pawn may capture diagonally onto the square the enemy pawn skipped. The captured pawn is removed. If you do not take it immediately, the right disappears. You cannot save it for a later turn.

Promotion: a pawn becomes something else

When a pawn reaches the far rank, it must be promoted to a queen, rook, bishop, or knight. The pawn does not stay a pawn, and promotion is part of the move. A player may have more than one queen; there is no limit on promoted pieces beyond the board.

A queen is the usual choice because it is the most powerful piece. A knight is occasionally better because it moves differently and can create an immediate fork. A rook or bishop is rarely the best choice, but both are legal. You may not promote to a king.

• Promotion happens on the eighth rank for White and the first rank for Black.
• Choose the piece as part of the move; you cannot defer the choice.
• A captured promoted piece is simply removed like any other piece.
• Underpromotion is legal and sometimes the strongest move.

Check is not a special move

Check is simply an attack on the king. When the king is in check, the next move must remove the attack: move the king, block the line, or capture the attacking piece. You may not ignore check, and you may not make a move that leaves your own king in check.

Checkmate is check with no legal escape. Stalemate is no legal move with no check. The difference matters: checkmate wins; stalemate draws.

How to remember them

For castling, check the king first: has it moved, is it in check, does it cross an attacked square, does it land on one? Then check the rook and the empty squares. For en passant, ask whether the enemy pawn just moved two squares. For promotion, remember that the choice is part of the move.

Set up each position on a board and play the move once. A rule you have physically moved is easier to remember than a rule you have only read.

The complete rules →How these moves are written →