The exchange (chess)

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In chess, the exchange is the material difference of a rook for a minor piece (i.e. a bishop or knight). Having a rook for a minor piece is generally advantageous, since the rook is usually more valuable. A player who has a rook for a minor piece is said to be up the exchange, and the other player is down the exchange. A player who wins a rook for a minor piece is said to have won the exchange, while the other player has lost the exchange. The opposing captures often happen on consecutive moves, but this is not strictly necessary. Although it is generally detrimental to lose the exchange, one may occasionally find reason to purposely do so; the result is an exchange sacrifice.

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"The exchange" differs from the more general "exchange" or "an exchange", which refers to the loss and subsequent gain of arbitrary pieces; for example, to "exchange queens" would mean that each side's queen is captured . [1]

The minor exchange is the exchange of a bishop for a knight. This term is rarely used.

Value of the exchange

The value of the exchange (i.e. the difference between a rook and a minor piece) 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 José 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. [2] Cecil Purdy said that the value depends on the total number of pawns on the board. The reason is that when there are many pawns, the rooks will have limited mobility because there will not be open files . The exchange is barely worth 1½ points when there are 14 or more pawns on the board. Only when there are ten or fewer pawns may the exchange be worth 2 points . [3] Purdy gave the value as 1½ points in the opening and increasing to 2 points in the endgame. In the middlegame the value would be closer to 1½ than to 2. [4] Edmar Mednis gave the value as 1½ in the endgame. [5] [6] Max Euwe put the value at 1½ in the middlegame and said that two pawns are more than sufficient compensation for the exchange. [7] 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 . [8] 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. [9] In practice, one pawn may be sufficient compensation for the loss of the exchange, whereas two pawns almost always is. [10]

In the endgame

In the middlegame, the advantage of the exchange is usually enough to win the game if the side with the rook has one or more pawns. In an endgame without pawns, the advantage of the exchange is normally not enough to win (see pawnless chess endgame). The most common exceptions when there are no pawns 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. [11]

In the endgame of a rook and a pawn versus a knight and a pawn, if the pawns are passed the rook is much stronger and should win. If the pawns are not passed, the side with knight has good drawing chances if its pieces are well-placed. [12]

In the endgame of a rook and a pawn versus a bishop and pawn, if the pawns are on the same file, the bishop has good chances to draw if the pawns are blocked and the opposing pawn is on a square the bishop can attack; otherwise the rook usually wins. If the pawns are passed the rook normally wins. If the pawns are not passed and are on adjacent files, it is difficult to assess but the bishop may be able to draw. [13]

Adams vs. Fine, 1940
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Black to move wins

In an endgame with more pawns on the board (i.e. a rook and pawns versus a minor piece with the same number of pawns) the rook usually wins. [14] This position is typical. The superior side should remember these things:

  1. the main idea is to get the king through to capture opposing pawns
  2. force as many opposing pawns as possible onto the same color square as the bishop
  3. some pawn exchanges may be necessary to open files , but keep pawns on both sides of the board
  4. try to keep the position unbalanced. A passed pawn almost immediately becomes a winning advantage. [15]

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. [16]

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 captures a knight on c3 with a rook), 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 A Yurgis–Botvinnik, 1931 [17] ), 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. When they do occur in the endgame, it is usually to create and promote a passed pawn. [18] Subsequently, the relative importance of the pieces might be different from 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 one's own minor pieces by eliminating opposition from their counterparts (such as in the Petrosian versus Spassky game below, 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, as frequently demonstrated by former world champion Tigran Petrosian.

Sokolov vs. Kramnik

Sokolov vs. Kramnik
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Position before 33.Rxc7!

In this 2004 game [19] between Ivan Sokolov and World Champion Vladimir Kramnik, White gave up the exchange for a pawn to create two strong connected passed pawns. The game continued:

33. Rxc7! Qxc7
34. Rxf6 Rxf6
35. Qxf6 Rf8

and White won on move 41. [20]

Reshevsky vs. Petrosian

Reshevsky vs. Petrosian
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Position before 25...Re6!!

Tigran Petrosian, the World Champion from 1963 to 1969, was well known for his especially creative use of this device. He once responded (only half jokingly), when asked what was his favourite piece, as saying "The rook, because I can sacrifice it for minor pieces!"[ citation needed ] In the game Reshevsky versus Petrosian at the 1953 Candidates Tournament in Zurich, [21] he sacrificed the exchange on move 25, only for his opponent to sacrifice it in return on move 30. This game is perhaps the most famous and most frequently taught example of the exchange sacrifice.

There are no open files in this position for the rooks to exploit. Black sacrificed the exchange with

25... Re6!!

With the rook not on e7, the black knight will be able to get to a strong outpost on d5. From there the knight will be attacking the pawn on c3, and if the white bishop on b2 does not move to d2, it will be of little use. In addition, it will be practically impossible to break Black's defense on the white squares. The next few moves were:

26. a4?! Ne7!
27. Bxe6 fxe6
28. Qf1! Nd5
29. Rf3 Bd3
30. Rxd3 cxd3

The game was drawn on move 41. [22]

Petrosian vs. Spassky

Petrosian vs. Spassky, 1966
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Position after 20...Bh3, before 21.Ne3!
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Position before 24.Rxf4!

In the tenth game from the 1966 World Chess Championship between defending champion Tigran Petrosian and challenger Boris Spassky contained two exchange sacrifices by White. [23] Black had just moved

20... Bh3?! (first diagram)

White responded with an exchange sacrifice:

21. Ne3!

White had no choice: 21.Rf2? Rxf4 22.Rxf4 Qg5+, etc. The game continued:

21... Bxf1? 22. Rxf1 Ng6 23. Bg4! Nxf4?! (second diagram)

And now a second exchange sacrifice:

24. Rxf4! Rxf4

Black is helpless, despite being two exchanges ahead. White won back an exchange on move 29. On move 30 White forced the win of the other rook and the exchange of queens. Black resigned because the position was a winning endgame for White (two knights and five pawns versus one knight and four pawns). [24] Petrosian won the match by one game to retain his title.

Kasparov vs. Shirov

Kasparov vs. Shirov
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Position before 17.Rxb7!!

In a 1994 game between World Champion Garry Kasparov and Alexei Shirov, [25] White sacrificed a pure exchange (rook for a bishop) with the move 17. Rxb7!!. As compensation for the sacrifice, Black became weak on the white squares, which were dominated by White's bishop. The exchange sacrifice also deprived Black of the bishop pair and his remaining bishop was a bad bishop . During the game, many spectating grandmasters were sceptical whether White's compensation was enough. Black returned the exchange on move 28, making the material equal, but White had a strong initiative. Black missed a better 28th move after which White could have forced a draw, but would have had no clear advantage. White won the game on move 38. [26]

Minor exchange

The minor exchange is the trade of the opponent's bishop for the player's knight (or, more recently, the stronger minor piece for the weaker). [27] Bobby Fischer used the term, [28] but it is rarely used.

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. In general, bishops have relatively higher value in an open game and knights have relatively higher value in a closed game .

Traditional chess theory espoused by masters such as Wilhelm Steinitz and Siegbert Tarrasch puts more value on the bishop than the knight. In contrast, 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. [29]

Occasions when a knight can be worth more than a bishop are frequent, so this exchange is not necessarily made at every opportunity to do so.

Black to move
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The bishop pair and two pawns in return is often more than sufficient compensation for the loss of the exchange.

Many of the Classicists of the late nineteenth and early twentieth century claimed that two bishops versus rook and knight were equivalent. Today, the view is that a pair of bishops shouldn't be underestimated, but the rook and knight are still superior. A pair of active bishops is frequently adequate compensation for a pawn - or even the exchange in a middlegame position. Adding the better cooperation of the rook with the bishops, many Soviet theoreticians believed that, in active positions, rook and two bishops outperform two rooks and a knight. The modern consensus is that the side with the two bishops need at least a pawn when facing rook and knight, even then the side with the two bishops is underdog. William Steinitz reckoned that often two bishops and two pawns are superior against rook and knight.

A rook and bishop usually work better together than a rook and knight in the endgame. [30] [31] José Raúl Capablanca stated that a queen and knight work better together than a queen and bishop in the endgame. [32] More recently, John Watson has stated that from his study of this endgame that an unusually large proportion of queen and knight versus queen and bishop endings are drawn, and that most decisive games are characterized by the winning side having one or more obvious advantages (for example, having a knight against a bad bishop in a closed position, or having a bishop in a position with pawns on both sides of the board, particularly if the knight has no natural outpost). Watson states that positions in this endgame in general "are very volatile, and often the winning side is simply the one who starts out being able to win material or launch an attack on the opposing king". [33] Glenn Flear agrees with that assessment for endgames. He could not find an endgame by Capablanca that supported his statement. The statistics for queen and bishop versus queen and knight endgames are about even. Most decisive games were won because of a significant advantage from the middlegame and only a limited number of positions show an inherent superiority for one over the other. [34]

See also

Related Research Articles

Chess strategy is the aspect of chess play concerned with evaluation of chess positions and setting goals and long-term plans for future play. While evaluating a position strategically, a player must take into account such factors as the relative value of the pieces on the board, pawn structure, king safety, position of pieces, and control of key squares and groups of squares. Chess strategy is distinguished from chess tactics, which is the aspect of play concerned with the move-by-move setting up of threats and defenses. Some authors distinguish static strategic imbalances, which tend to persist for many moves, from dynamic imbalances, which are temporary. This distinction affects the immediacy with which a sought-after plan should take effect. Until players reach the skill level of "master", chess tactics tend to ultimately decide the outcomes of games more often than strategy. Many chess coaches thus emphasize the study of tactics as the most efficient way to improve one's results in serious chess play.

<span class="mw-page-title-main">Bishop (chess)</span> Chess piece

The bishop is a piece in the game of chess. It moves and captures along diagonals without jumping over interfering pieces. Each player begins the game with two bishops. The starting squares are c1 and f1 for White's bishops, and c8 and f8 for Black's bishops.

The endgame is the final stage of a chess game which occurs after the middlegame. It begins when few pieces are left on the board.

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 chess, a relative value is a standard value conventionally assigned to each piece. Piece valuations have no role in the rules of chess but are useful as an aid to assessing a position.

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.

In chess, compensation is the typically short-term positional advantages a player gains in exchange for typically material disadvantage. Short-term advantages involve initiative and attack.

<span class="mw-page-title-main">Tarrasch rule</span> General principle in chess

The Tarrasch rule is a general principle that applies in the majority of chess middlegames and endgames. Siegbert Tarrasch (1862–1934) stated the "rule" that rooks should be placed behind passed pawns – either the player's or the opponent's. The idea behind the guideline is that (1) if a player's rook is behind their own passed pawn, the rook protects it as it advances, and (2) if it is behind an opponent's passed pawn, the pawn cannot advance unless it is protected along its way.

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 safe 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.

In chess, a desperado is a piece that is either en prise or trapped, but captures an enemy piece before it is itself captured in order to compensate the loss a little, or is used as a sacrifice that will result in stalemate if it is captured. The former case can arise in a situation where both sides have hanging pieces, in which case these pieces are used to win material prior to being captured. A desperado in the latter case is usually a rook or a queen; such a piece is sometimes also called crazy or mad.

<span class="mw-page-title-main">Swindle (chess)</span> Chess maneuver

In chess, a swindle is a ruse by which a player in a losing position tricks their opponent and thereby achieves 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 those bishops operate on opposite-colored squares. Without other pieces besides pawns and the kings, 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 still not as many as when bishops are on the same color.

A pawnless chess endgame is a chess endgame in which only a few pieces remain, and no pawns. The basic checkmates are types of pawnless endgames. Endgames without pawns do not occur very often in practice except for the basic checkmates of king and queen versus king, king and rook versus king, and queen versus rook. Other cases that occur occasionally are (1) a rook and minor piece versus a rook and (2) a rook versus a minor piece, especially if the minor piece is a bishop.

Much literature about chess endgames has been produced in the form of books and magazines. A bibliography of endgame books is below.

<span class="mw-page-title-main">Chess theory</span> Basic chess fundamentals and ideas developed to better understand the game

The game of chess is commonly divided into three phases: the opening, middlegame, and endgame. There is a large body of theory regarding how the game should be played in each of these phases, especially the opening and endgame. Those who write about chess theory, who are often also eminent players, are referred to as "chess theorists" or "chess theoreticians".

In a chess endgame of a king, bishop, and pawn versus a bare king, or, less commonly, a king, rook, and pawn versus a bishop and king, a wrong rook pawn is a rook pawn whose promotion square is the opposite color from the bishop's square color. Since a side's rook pawns promote on opposite-colored squares, and a bishop can only move on one color, one of the pawns may be the "wrong rook pawn". This situation is also known as having the wrong-colored bishop or wrong bishop. In many cases, the wrong rook pawn will only draw, when any other pawn would win. This is because the defending side can sometimes get their king to the corner in front of the pawn, after which the attacking side cannot chase the king away to enable promotion. A fairly common defensive tactic is to reach one of these drawn endgames, often through a sacrifice.

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.

<span class="mw-page-title-main">Outline of chess</span> Strategy board game

The following outline is provided as an overview of and topical guide to chess:

References

  1. ( Hooper & Whyld 1992 , p. 130)
  2. ( Soltis 2004 :110)
  3. ( Soltis 2004 :134)
  4. ( Purdy 2003 :146–52)
  5. ( Mednis 1978 :120)
  6. ( Mednis 1987 :107)
  7. ( Euwe & Kramer 1994 :38)
  8. ( Soltis 2004 :110)
  9. ( Berliner 1999 :14)
  10. ( Soltis 2004 :110)
  11. ( Nunn 2002 :9, 31)
  12. ( Müller & Lamprecht 2001 :260–63)
  13. ( Müller & Lamprecht 2001 :274–79)
  14. ( Müller & Lamprecht 2001 :256–91)
  15. ( Fine & Benko 2003 :478–79)
  16. ( Fine & Benko 2003 :478ff)
  17. "A Yurgis vs. Botvinnik, 1931". Chessgames.com .
  18. ( Soltis 2004 :115)
  19. "Ivan Sokolov vs. Vladimir Kramnik (2004)". Chessgames.com .
  20. ( Soltis 2004 :110)
  21. "Reshevsky vs. Petrosian, 1953". Archived from the original on 2009-12-01. Retrieved 2009-04-26.
  22. ( Kasparov 2004 :14)
  23. "Tigran V Petrosian vs. Boris Spassky (1966)". Chessgames.com .
  24. ( Kasparov 2004 :72–74)
  25. "Garry Kasparov vs. Alexey Shirov (1994)". Chessgames.com .
  26. ( Nunn 2001 :149–58)
  27. ( Soltis 2004 :169)
  28. ( Benko 2007 :192, 199, 216)
  29. ( Mayer 1997 :7)
  30. ( Mayer 1997 :201–8)
  31. ( Beliavsky & Mikhalchishin 2000 :141)
  32. ( Mayer 1997 :209–18)
  33. ( Watson 1998 :73)
  34. ( Flear 2007 :422)

Bibliography

Further reading