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
Evolution of the horse horse", "Orohippus" was not a true horse and did not live in the mountains. It resembled "Eohippus" in size, but had a slimmer body, an elongated head, slimmer forelimbs, and longer hind legs, all of which are characteristics of a good jumper. Although "Orohippus" was still pad-footed, the vestigial outer toes of "Eohippus" were not present in "Orohippus"; there were four toes on each fore leg, and three on each hind leg. The most dramatic change between "Eohippus" and "Orohippus" was in the teeth: the first of the premolar teeth were dwarfed, the last premolar shifted in shape and function