Mined squares

Mined squares occur mainly in blocked pawn endings. They are not necessarily attacked or illegal. They are dangerous because stepping onto one permits an exact reply by the opposing king.

They normally form a pair. If one king enters the first square, the other king occupies the corresponding square. That reply creates zugzwang, a position in which the player who must move loses a key square, a pawn, or access to part of the board. This is why walking around an apparently natural square can be correct.

Mined squares are the simplest case of corresponding squares. Two squares correspond when occupying one requires the opponent to answer on the other to preserve the result. More complex positions may contain several pairs and routes between them rather than one obvious pair.

A square may stop being mined after the pawn structure changes, a pawn moves, or one king loses access to the matching reply. The concept describes a dynamic relationship between two squares and the move, not a permanent property printed on the board.