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
Atomic chess at Chess Live and Internet Chess Club in 2000, Free Internet Chess Server in 2003 and Lichess in 2015. Rules of atomic chess are the same as standard chess with a few important differences concerning capturing, check, and winning conditions. In standard chess, the captured piece is removed from the board and the capturing piece takes its place. In atomic chess, a capture causes an "explosion" through which both pieces are removed from the board as well as all non-pawn pieces in the eight squares immediately surrounding the capture. Pawns are removed only when capturing, captured directly, or promoted. In