[blind-chess] Chess Article #66: The Exchange in Chess (fwd)
- From: Roderick Macdonald <rmacd@xxxxxxxx>
- To: Blind Chess Mailing List <blind-chess@xxxxxxxxxxxxx>
- Date: Mon, 28 Jun 2010 16:41:18 -1000 (HST)
Chess Article #66:
The exchange in chess
Adapted and Condensed from
Wikipedia, the Free Encyclopedia
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.
++1. Value of the exchange
The value of the exchange has been considered for decades. Siegbert
Tarrasch put its value as 1.5 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 greater
than 1 pawn, but only less than 1 pawn if the player with the minor
piece has the bishop pair (Soltis 2004:110ff). 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 (Berliner
1999:14). In practice, one pawn may be sufficient compensation for
the loss of the exchange, whereas two pawns almost always is
(Soltis 2004:110ff).
++2. 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. 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.
Diagram #1:
White: King at d2, Bishop at c6, Pawns at a2, b2, c2, d3, g2, 82
Black: King at f8, Rook at d8, Pawns at a7, b6, c5, f7, g6, h7
Adams-Fine, 1940
Black to move wins
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 (M`uller &
Lamprecht 2001:256-91). This position is typical. The superios ride
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 advangage ]Fine & Benko
2003:478-79).
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 (Fine &
Benko 2003:478ff).
++3. 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 A Yurgis
vs Botvinnik, 1931), 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 point 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 Petrosian vs Spassky, 1966 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.
++4. 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 (Mayer 1997:7).
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 (Mayer 1997:201-8), (Beliavsky &
Mikhalchishin 2000:141). Jose Capablanca stated that a queen and
knight work better together than a queen and bishop in the endgame
(Mayer 1997:209-18).
==========
The blind-chess mailing list
View list information and change your settings: //www.freelists.org/list/blind-chess
List archives: //www.freelists.org/archives/blind-chess
=========
Other related posts:
- » [blind-chess] Chess Article #66: The Exchange in Chess (fwd) - Roderick Macdonald
