How the king moves
The king moves exactly one square: forward, backward, sideways or diagonally. It may never move onto a square attacked by an enemy piece, and it may never stay in check. That is also why the two kings can never stand on neighbouring squares.
Castling is the king's one special move. The king moves two squares toward a rook, and the rook jumps over to the square beside it. It is only legal if neither piece has moved, the squares between them are empty, the king is not in check, and it does not pass through or land on an attacked square.
Check, checkmate and stalemate
A king attacked by an enemy piece is in check, and its side must get out of check at once: by moving the king, capturing the attacker, or blocking the line. If none of those is possible, it is checkmate and the game is over.
If the side to move is not in check but has no legal move at all, it is stalemate, and the game is a draw. Stalemate traps are a common way for the defending side to save a lost position.
How to use your king well
In the opening and middlegame, keep the king safe. Castling early tucks it behind a wall of pawns and brings a rook toward the centre. Avoid pushing the pawns in front of your castled king without a reason.
In the endgame the king becomes a strong fighting piece. With fewer pieces left there is less danger of mate, so march it to the centre, use it to support passed pawns and to stop the enemy's, and remember that opposition between the kings often decides king and pawn endings.
Common mistakes
- Delaying castling and getting caught in the centre when the position opens.
- Leaving the king passive in the endgame instead of using it as an active piece.
- Stalemating the opponent when you are winning, by taking away the last legal moves without giving check.
Questions about the king
Can the king capture?
Yes, it can capture an adjacent enemy piece, but only if that piece is not defended, because the king can never move into check.
Can a king take another king?
No. The kings can never stand next to each other, because each would be moving into check.
Can you castle out of check?
No. You cannot castle while in check, through an attacked square, or onto an attacked square.
Can the king move two squares?
Only when castling. Otherwise the king always moves one square at a time.
Practise every piece on a live board in the rules of chess, and read more about castling, check and checkmate and stalemate.