Undermining (chess) Undermining (chess) Undermining (also known as removal of the guard, or removing the defender) is a chess tactic in which a defensive piece is captured, leaving one of the opponent's pieces undefended or under-defended. The opponent has the unpalatable choice of recapturing or saving the undefended piece. A possible response is to sacrifice the piece whose defense was undermined before capturing the piece which just took the defender. Kramnik–Topalov in the seventh round of the 2004 Linares chess tournament reached the diagrammed position with White to play. The black knight on a4 is defended only by the black pawn on
Chess piece play, pieces of the Staunton chess set design are standard. The height of the king should be between . United States Chess Federation rules call for a king height between . A height of about is preferred by most players. The diameter of the king should be 40–50% of its height. The size of the other pieces should be in proportion to the king. The pieces should be well balanced such that their center of gravity is closer to the board. This is done by adding weights such as iron studs or lead blocks at the bottom and felted. It