King

The king is the piece each player must protect, because the game ends when it is attacked and no permitted reply exists. That situation is called checkmate . Each side has one king. White's begins on e1, the square in vertical column e and horizontal row 1; Black's begins on e8, the same column in row 8.

Normally, the king moves one square in any direction and may capture an enemy piece on its destination. That destination cannot be attacked by the opponent. For the same reason, the two kings can never stand on adjacent squares, because each would attack the other. Castling is a special exception in which the king moves two squares and a rook also changes position.

The king and its safe destinations

8

7

6

5

4

3

2

a1

b

c

d

e

f

g

h

c5, d5, e4, and e5 are adjacent, but they are attacked and are not legal destinations.

Eight adjacent squares, different legality

The king on d4 has eight adjacent squares. c3 and d3 are empty and safe destinations. c4 is occupied by a friendly piece. c5, d5, e4, and e5 are attacked by Black. On e3, the king may capture the black pawn because the square is safe after the pawn is removed.

1. c5, d5, e4, and e5 are adjacent, but they are attacked and are not legal destinations.
2. c3 and d3 are empty, safe, and available to the king.
3. The king may capture the pawn on e3 because the square is safe after the capture.
4. The friendly pawn on c4 prevents the king from occupying that square.

When an enemy piece attacks the king, the king is in check . The player must make a legal move, meaning one permitted by all the rules, that removes the threat: move the king, capture the attacker, or, when a distant attack follows a horizontal row, vertical column, or diagonal with a square in between, place another piece in the way.

If no legal response exists, the position is checkmate. Any move that leaves one's own king attacked is an illegal move.