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The exchange (chess)
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The exchange in chess refers to a situation in which one player loses a minor piece (i.e. a bishop or knight) but captures the opponent's rook. The side which wins the rook is said to have won the exchange, while the other player has lost the exchange, since the rook is usually more valuable. Subsequently, the side that has won the rook is up the exchange, and the other player is down the exchange.
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The exchange in chess refers to a situation in which one player loses a minor piece (i.e. a bishop or knight) but captures the opponent's rook. The side which wins the rook is said to have won the exchange, while the other player has lost the exchange, since the rook is usually more valuable. Subsequently, the side that has won the rook is up the exchange, and the other player is down the exchange. The opposing captures often happen on consecutive moves, although this is not strictly necessary. It is generally detrimental to lose the exchange, although occasionally one may find reason to purposely do so; the result is an exchange sacrifice (see below). The minor exchange is a less common term for the exchange of a bishop and knight (see below).
Note that the exchange differs from the more general "exchange" or "an exchange," which refers to the loss and subsequent gain of arbitrary pieces.
Value of the exchange
The value of the exchange has been considered for decades. Siegbert Tarrasch put its value as 1½ pawns in the endgame, but not for the opening or the first part of the middlegame. That is widely accepted today, but Jacob Sarratt, Howard Staunton, and Jose Capablanca felt that the exchange was worth two pawns. Tigran Petrosian thought that one pawn was the right value. Wilhelm Steinitz said that a rook is slightly better than a knight and two pawns but slightly worse than a bishop and two pawns. Cecil Purdy said that the value depends on the total number of pawns on the board. Larry Kaufman's computer research puts the value as 1¾ pawns, but only 1¼ pawns if the player with the minor piece has the bishop pair . Hans Berliner puts the difference between a rook and knight as 1.9 pawns and the difference between a rook and a bishop as 1.77 pawns . In practice, one pawn may be sufficient compensation for the loss of the exchange, whereas two pawns almost always is .
In the endgame
In the middlegame, the advantage of an exchange is usually enough to win the game. In an endgame without pawns, the advantage of the exchange is normally not enough to win (see pawnless chess endgames). The most common exceptions are (1) a rook versus a bishop in which the defending king is trapped in a corner of the same color as his bishop, (2) a knight separated from its king that may be cornered and lost, and (3) the king and knight are poorly placed.
With pawns on the board (i.e. a rook and pawns versus a minor piece with the same number of pawns) the rook usually wins . This position is typical. The superior side should remember these things:
- the main idea is to get the king through to capture opposing pawns
- force as many opposing pawns as possible onto the same color square as the bishop
- some pawn exchanges may be necessary to open files, but keep pawns on both sides of the board
- try to keep the position unbalanced. A passed pawn almost immediately becomes a winning advantage .
If the minor piece has an extra pawn (i.e. one pawn for the exchange), the rook should win, but with difficulty. If the minor piece has two extra pawns, the endgame should be a draw .
The exchange sacrifice
An exchange sacrifice occurs when one player gives up a rook for a minor piece. It is often used to destroy the enemy pawn structure (as in several variations of the Sicilian Defence where Black plays RxNc3), to establish a minor piece on a strong square (often threatening the enemy king), to improve one's own pawn structure (creating, for example, connected passed pawns such as in ), or to gain time for development. The exchange sacrifice contrasts with other sacrifices in that during the early-middle to middle game the board is sufficiently crowded to where the rook is not as effective as an active knight or a good bishop, this is why such exchange sacrifices happen usually from moves 20 to 30, and rarely occur in the later moves. Subsequently the relative importance of the pieces might be different than the standardized Chess piece relative value system and takes advantage of the fluctuating values of the pieces during the progression of the game. The sacrifice might also be used to increase the influence of ones own minor pieces by eliminating opposition from their counterparts. (such as in where even a double exchange sacrifice was successful) A common example of this idea is the elimination an opponent’s bishop, with the expectation that in doing so one’s own bishop will increase in power from being unopposed on the color squares in which it resides. There is often more dynamic play and positional considerations such as pawn structure or piece placement compared to sacrifices due to a mating attack or a pawn sacrifice to gain the initiative. Sometimes the exchange can be sacrificed purely on long term positional objectives.Tigran Petrosian, the world Champion from 1963-1969, was well known for his especially creative use of this device. He was once responded (only half jokingly), when asked what was his favourite piece, as saying "The rook, because I can sacrifice it for minor pieces!" In the game Reshevsky-Petrosian, Zurich 1953, he sacrificed the exchange on move 25, only for his opponent to sacrifice it in return on move 30 (the game ended in a draw); this game is perhaps the most famous and most frequently taught example of the exchange sacrifice.
Minor exchange (bishop for knight)
The minor exchange refers to the capture of the opponent's bishop for the player's knight (or, more recently, the stronger minor piece for the weaker). The term is rarely used. It can also refer to the capture of two of the opponent's minor pieces for the player's rook.
In most chess positions, a bishop is worth slightly more than a knight because of its longer range of movement. As a chess game progresses, pawns tend to get traded, removing support points from the knight and opening up lines for the bishop. This generally leads to the bishop's advantage increasing over time.
Traditional chess theory espoused by masters such as Wilhelm Steinitz and Siegbert Tarrasch puts more value on the bishop than the knight. The hypermodern school favored the knight over the bishop. Modern theory is that it depends on the position, but that there are more positions where the bishop is better than where the knight is better .
There are some occasions when a knight can be worth more than a bishop, so this exchange is not necessarily made at every opportunity to do so.
A rook and bishop usually work better together than a rook and knight in the endgame , . Jose Capablanca stated that a queen and knight work better together than a queen and bishop in the endgame .
Related articles
- Chess piece relative value
See also
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