The knight is a piece in the game of chess, represented by a horse's head and neck. It may move two squares vertically and one square horizontally or two squares horizontally and one square vertically. Each player starts the game with two knights on the b- and g-files, each located between a rook and a bishop.
In the game of chess, perpetual check is a situation in which one player can force a draw by an unending series of checks. This typically arises when the player who is checking cannot deliver checkmate, and failing to continue the series of checks gives the opponent at least a chance to win. A draw by perpetual check is no longer one of the rules of chess; however, such a situation will eventually allow a draw claim by either threefold repetition or the fifty-move rule. Players usually agree to a draw long before that, however.
Zugzwang is a situation found in chess and other turn-based games wherein one player is put at a disadvantage because of their obligation to make a move; a player is said to be "in zugzwang" when any legal move will worsen their position.
In the game of chess, an endgame study, or just study, is a composed position—that is, one that has been made up rather than played in an actual game—presented as a sort of puzzle, in which the aim of the solver is to find the essentially unique way for one side to win or draw, as stipulated, against any moves the other side plays. If the study does not end in a mate or stalemate, it should be obvious that the game is either won or drawn, and White can have a selection of many different moves. There is no limit to the number of moves which are allowed to achieve the win; this distinguishes studies from the genre of direct mate problems. Such problems also differ qualitatively from the very common genre of tactical puzzles based around the middlegame, often based on an actual game, where a decisive tactic must be found.
The Lucena position is one of the most famous and important positions in chess endgame theory, where one side has a rook and a pawn and the defender has a rook. Karsten Müller said that it may be the most important position in endgame theory. It is fundamental in the rook and pawn versus rook endgame. If the side with the pawn can reach this type of position, they can forcibly win the game. Most rook and pawn versus rook endgames reach either the Lucena position or the Philidor position if played accurately. The side with the pawn will try to reach the Lucena position to win; the other side will try to reach the Philidor position to draw.
The two knights endgame is a chess endgame with a king and two knights versus a king. In contrast to a king and two bishops, or a bishop and a knight, a king and two knights cannot force checkmate against a lone king. Although there are checkmate positions, a king and two knights cannot force them against proper, relatively easy defense.
Triangulation is a tactic used in chess to put one's opponent in zugzwang. Triangulation is also called losing a tempo or losing a move.
The chess endgame with a king and a pawn versus a king is one of the most important and fundamental endgames, other than the basic checkmates. It is an important endgame for chess players to master, since most other endgames have the potential of reducing to this type of endgame via exchanges of pieces. Players need to be able to determine quickly whether a given position is a win or a draw, and to know the technique for playing it. The crux of this endgame is whether or not the pawn can be promoted, so checkmate can be forced.
In chess, a fortress is an endgame drawing technique in which the side behind in material sets up a zone of protection that the opponent cannot penetrate. This might involve keeping the enemy king out of one's position, or a zone the enemy cannot force one out of. An elementary fortress is a theoretically drawn position with reduced material in which a passive defense will maintain the draw.
The bishop and knight checkmate in chess is the checkmate of a lone king which can be forced by a king, a bishop, and a knight. With the stronger side to move and with perfect play, checkmate can be forced in at most thirty-three moves from any starting position where the defender cannot quickly win one of the pieces. The exception is the "stalemate trap". These exceptions constitute about 0.5% of the positions. Checkmates are possible with the defending king on any square at the edge of the board but can be forced only from positions with different material or if the defending king is in a corner controlled by the bishop or on a square on the edge next to a corner; however, mate adjacent to the corners not controlled by the bishop is only two moves deep, so it is not generally encountered unless the defending side plays inaccurately. Although this is classified as one of the four basic or elementary checkmates, it occurs in practice only approximately once in every 6,000 games.
The rook and pawn versus rook endgame is a fundamentally important, widely studied chess endgame. Precise play is usually required in these positions. With optimal play, some complicated wins require sixty moves to either checkmate, capture the defending rook, or successfully promote the pawn. In some cases, thirty-five moves are required to advance the pawn once.
In chess, a blunder is a critically bad move. It is usually caused by some tactical oversight, whether it be from time trouble, overconfidence or carelessness. Although blunders are more common in amateur games, all human players make them, even at the world championship level. Giving the opponent opportunities to blunder is an important skill in over the board chess.
The chess endgame of a queen versus pawn is usually an easy win for the side with the queen. However, if the pawn has advanced to its seventh rank it has possibilities of reaching a draw, and there are some drawn positions with the pawn on the sixth rank. This endgame arises most often from a race of pawns to promote.
In chess, two squares are corresponding squares if the occupation of one of these squares by a king requires the enemy king to move to the other square in order to hold the position. Corresponding squares exist in some chess endgames, usually ones that are mostly blocked. Usually, there are several groups of corresponding squares. In some cases, they indicate which square the defending king must move to in order to keep the opposing king away. In other cases, a maneuver by one king puts the other player in a situation where he cannot move to the corresponding square, so the first king is able to penetrate the position. The theory of corresponding squares is more general than opposition and is more useful in cluttered positions.
In chess, a swindle is a ruse by which players in a losing position trick their opponent and thereby achieve a win or draw instead of the expected loss. It may also refer more generally to obtaining a win or draw from a clearly losing position. I. A. Horowitz and Fred Reinfeld distinguish among "traps", "pitfalls", and "swindles". In their terminology, a "trap" refers to a situation where players go wrong through their own efforts. In a "pitfall", the beneficiary of the pitfall plays an active role, creating a situation where a plausible move by the opponent will turn out badly. A "swindle" is a pitfall adopted by a player who has a clearly lost game. Horowitz and Reinfeld observe that swindles, "though ignored in virtually all chess books", "play an enormously important role in over-the-board chess, and decide the fate of countless games".
The opposite-colored bishops endgame is a chess endgame in which each side has a single bishop and the bishops reside on opposite-colored squares on the chessboard and thus cannot attack or block each other. Without other pieces these endings are widely known for their tendency to result in a draw. These are the most difficult endings in which to convert a small material advantage to a win. With additional pieces, the stronger side has more chances to win, but not as many as when bishops are on the same color.
In chess, particularly in endgames, a key square is a square such that if a player's king can occupy it, he can force some gain such as the promotion of a pawn or the capture of an opponent's pawn. Key squares are useful mostly in endgames involving only kings and pawns. In the king and pawn versus king endgame, the key squares depend on the position of the pawn and are easy to determine. Some more complex positions have easily determined key squares while other positions have harder-to-determine key squares. Some positions have key squares for both White and Black.
The Réti endgame study is a chess endgame study by Richard Réti. It was published in 1921 in Kagans Neueste Schachnachrichten. It demonstrates how a king can make multiple threats and how it can take more than one path to a given location, using the same number of moves. It is covered in many books on the endgame. The procedure is known as the "Réti Maneuver" or "Réti's Idea", ,. Endgame composer Abram Gurvich called the theme "The Hunt of Two Hares" and it appears in many other studies and games. It is also called "chasing two birds at once".
The queen and pawn versus queen endgame is a chess endgame in which both sides have a queen and one side has a pawn, which one tries to promote. It is very complicated and difficult to play. Cross-checks are often used as a device to win the game by forcing the exchange of queens. It is almost always a draw if the defending king is in front of the pawn.
Chess on a really big board is a large chess variant invented by Ralph Betza around 1996. It is played on a 16×16 chessboard with 16 pieces and 16 pawns per player. Since such a board can be constructed by pushing together four standard 8×8 boards, Betza also gave this variant the alternative names of four-board chess or chess on four boards.
