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
Fork (chess) Fork (chess) In chess, a fork is a tactic whereby a single piece makes two or more direct attacks simultaneously. Most commonly two pieces are threatened, which is also sometimes called a "". The attacker usually aims to gain by one of the opponent's pieces. The defender often finds it difficult to counter two or more threats in a single move. The attacking piece is called the "forking" piece; the pieces attacked are said to be "forked". A piece that is defended can still be said to be forked if the forking piece has a lower value. Besides attacking pieces,