Check

A king is in check when one or more opposing pieces attack the square it occupies. The player must answer on that turn; the attack cannot be ignored, the turn cannot be skipped, and no move may leave the king under attack. Announcing check aloud is not required.

Ways to answer check

1. Move the king to a square that is not attacked.
2. Make a capture of the checking piece, provided the king is then safe.
3. Place a piece between the attacker and the king when the attack travels along a horizontal row, vertical column, or diagonal.

Not every method is available in every position. A check by a knight, pawn, or adjacent piece cannot be blocked because there is no square in between. If no reply is a legal move, the position is checkmate.

When deciding where a king may move, a square still counts as attacked even if the opposing piece controlling it could not move there without exposing its own king. This rule keeps the kings apart and can prevent a king from capturing an apparently restricted defender.