The king in chess moves one square in any direction: horizontally, vertically, or diagonally. However, it cannot move to a square occupied by a friendly piece or a square where it would be in check (under attack by an opponent's piece)

. Additionally, the king has a special move called castling, which involves moving the king two squares toward a rook on its original square, then placing that rook on the square the king crossed. Castling is only allowed if neither the king nor the rook has moved before, there are no pieces between them, the king is not currently in check, and the squares the king moves across are not under attack

. The king cannot move into check, cannot move adjacent to the opposing king, and captures by moving one square onto an enemy piece's square

. In summary:

• Moves one square in any direction (horizontal, vertical, diagonal)
• Cannot move into check or onto a square occupied by a friendly piece
• Can capture an enemy piece by moving onto its square
• Special move: castling with a rook under specific conditions

This makes the king the most important piece in chess, as checkmate (threatening the king with no escape) ends the game