Editing Chess strategy (section)

== Basic concepts of board evaluation ==
{{Main|Chess piece relative value}}

A {{chessgloss|material}} advantage applies both strategically and tactically. Generally more pieces or an aggregate of more powerful pieces means greater chances of winning. A fundamental strategic and tactical rule is to capture opponent pieces while preserving one's own.

Bishops and knights are called ''minor pieces''. A [[Knight (chess)|knight]] is about as valuable as a [[Bishop (chess)|bishop]], but less valuable than a [[Rook (chess)|rook]]. Rooks and the queen are called ''major pieces''. Bishops are usually considered slightly better than knights in open positions, such as toward the end of the game when many of the pieces have been captured, whereas knights have an advantage in closed positions. Having two bishops (the {{chessgloss|bishop pair}}) is a particularly powerful weapon, especially if the opposing player lacks one or both of their bishops.

Three [[Pawn (chess)|pawns]] are likely to be more useful than a knight in the [[Chess endgame|endgame]], but in the [[Chess middlegame|middlegame]], a knight is often more powerful. Two minor pieces are stronger than a single rook, and two rooks are slightly stronger than a queen. The bishop on squares of the same color as the opponent's king is slightly more valuable in the opening as it can attack the vulnerable square f7 (for White) or f2 (for Black). A rook is more valuable when {{chessgloss|doubled rooks|doubled}} with another rook or queen; consequently, doubled rooks are worth more than two {{chessgloss|connected rooks|unconnected rooks}}.

One commonly used simple scoring system is:
:{| class="wikitable"
! Piece !! Value
|-
| Pawn || align="center" | 1
|-
| Knight || align="center" | 3
|-
| Bishop || align="center" | 3
|-
| Rook || align="center" | 5
|-
| Queen || align="center" | 9
|}

Under a system like this, giving up a knight or bishop to win a rook ("winning [[the exchange (chess)|the exchange]]") is advantageous and is worth about two pawns. This ignores complications such as the current position and freedom of the pieces involved, but it is a good starting point. In an open position, bishops are more valuable than knights (a bishop pair can easily be worth seven points or more in some situations); conversely, in a closed position, bishops are less valuable than knights. A knight in the center of the board that cannot be taken, however, is known as a [[Outpost (chess)|knight outpost]] and threatens several [[fork (chess)|fork]] instances. In such a case, a knight is worth far more than a bishop. Also, many pieces have a partner. By doubling up two knights, two rooks, rook and queen, or bishop and queen, the pieces can get stronger than the sum of the individual pieces alone. When a piece loses its partner, its value slightly decreases. The [[king (chess)|king]] is priceless since its capture results in the defeat of that player and ends that game. However, especially in the endgame, the king can also be a fighting piece, and is sometimes given a fighting value of three-and-a-half points.

=== Space ===
Other things being equal, the side that controls more {{chessgloss|space}} on the board has an advantage.<ref>{{cite web|url=http://www.chessstrategyonline.com/content/tutorials/introduction-to-chess-strategy-positional-advantage|title=Positional advantage - Chess Strategy Online|website=www.chessstrategyonline.com|access-date=3 April 2018}}</ref> More space means more options, which can be exploited both tactically and strategically. A player who has all pieces developed and no tactical tricks or promising long-term plan should try to find a move that enlarges their influence, particularly in the center. In some openings, however, one player accepts less space for a time, to set up a counterattack in the middlegame. This is one of the concepts behind [[hypermodernism (chess)|hypermodern]] play.

The easiest way to gain space is to push the pawn skeleton forward. One must be careful not to over stretch, however. If the opponent succeeds in getting a protected piece behind enemy lines, this piece can become such a serious problem that a piece with a higher value might have to be exchanged for it.

{{Chess diagram
|tright
|
|rd|  |  |qd|  |rd|kd|  
|pd|bd|pd|nd|bd|pd|pd|pd
|  |pd|  |pd|  |nd|  |  
|  |  |  |pl|pd|  |  |  
|  |  |pl|  |pl|  |  |  
|pl|  |nl|  |  |  |pl|  
|  |pl|  |  |nl|pl|bl|pl
|rl|  |bl|ql|  |rl|kl|  
|White has an advantage in space.<ref name=Evans103 />
}}
[[Larry Evans (chess grandmaster)|Larry Evans]] gives a method of evaluating space. The method (for each side) is to count the number of squares attacked or occupied on the opponent's side of the board. In this diagram from the [[Nimzo-Indian Defense]], Black attacks four squares on White's side of the board (d4, e4, f4, and g4). White attacks seven squares on Black's side of the board (b5, c6, e6, f5, g5, and h6 – counting b5 twice) and occupies one square (d5). White has a space advantage of eight to four and Black is cramped.<ref name="Evans103">Evans (1958), pp. 103–04</ref>

===Control of the center===
{{chess diagram small
|tleft
|
|rd|nd|bd|qd|kd|bd|nd|rd
|pd|pd|pd|pd|pd|pd|pd|pd
| | | | | | | | 
| | | |xx|xx| | | 
| | | |xx|xx| | | 
| | | | | | | | 
|pl|pl|pl|pl|pl|pl|pl|pl
|rl|nl|bl|ql|kl|bl|nl|rl
|Center squares are marked by "X".
}}
The strategy consists of placing pieces so that they attack the central four squares of the board. A piece being placed on a central square, however, does not necessarily mean it controls the center; e.g., a knight on a central square does not attack any central squares. Conversely, a piece does not have to be on a central square to control the center. For example, the bishop can control the center from afar.

Control of the center is generally considered important because tactical battles often take place around the central squares, from where pieces can access most of the board. Center control allows more movement and more possibility for attack and defense.

Chess openings try to control the center while developing pieces. [[Hypermodernism (chess)|Hypermodern]] openings are those that control the center with pieces from afar (usually the side, such as with a [[fianchetto]]); the older Classical (or Modern) openings control it with pawns.
{{clear left}}

===Initiative===
{{Main|Initiative (chess)}}

The initiative belongs to the player who can make threats that cannot be ignored, such as checking the opponent's king. They thus put their opponent in the position of having to use their turns responding to threats rather than making their own, hindering the development of their pieces.<ref>{{cite web |url=http://chess.about.com/od/reference/g/bldefini.htm |title=Glossary : Initiative |access-date=2010-02-20 |url-status=dead |archive-url=https://web.archive.org/web/20060506002514/http://chess.about.com/od/reference/g/bldefini.htm |archive-date=2006-05-06 }}</ref> The player with the initiative is generally attacking and the other player is generally defending.

=== Defending pieces ===
It is important to defend one's pieces even if they are not directly threatened. This helps stop possible future campaigns from the opponent. If a defender must be added at a later time, this may cost a [[Tempo (chess)|tempo]] or even be impossible due to a fork or discovered attack. The approach of always defending one's pieces has an antecedent in the theory of [[Aron Nimzowitsch]] who referred to it as "overprotection." Similarly, if one spots undefended enemy pieces, one should immediately take advantage of those pieces' weakness.

Even a defended piece can be vulnerable. If the defending piece is also defending something else, it is called an overworked piece, and may not be able to fulfill its task. When there is more than one attacking piece, the number of defenders must also be increased, and their values taken into account. In addition to defending pieces, it is also often necessary to defend key squares, open files, and the {{chessgloss|back rank}}. These situations can easily occur if the [[pawn structure]] is weak.

=== Exchanging pieces ===
{{Main|Exchange (chess)}}

To exchange pieces means to capture a hostile piece and then allow a piece of the same value to be captured. As a rule of thumb, exchanging pieces eases the task of the defender who typically has less room to operate in.

Exchanging pieces is usually desirable to a player with an existing advantage in material, since it brings the endgame closer and thereby leaves the opponent with less ability to recover ground. In the endgame even a single pawn advantage may be decisive. Exchanging also benefits the player who is being attacked, the player who controls less space, and the player with the better pawn structure.{{Citation needed|date=July 2010}}

When playing against stronger players, many beginners attempt to constantly exchange pieces "to simplify matters". However, stronger players are often relatively stronger in the endgame, whereas errors are more common during the more complicated middlegame.

Note that "[[the exchange (chess)|the exchange]]" may also specifically mean a rook exchanged for a bishop or knight. The phrase "up the exchange" means that a player has captured a rook in exchange for a bishop or knight—a materially advantageous trade. Conversely, "down the exchange" means having lost a rook but captured a bishop or knight—a materially disadvantageous trade.

===Specific pieces===

==== Pawns ====
{{Main|Pawn (chess)|l1=Pawn|Pawn structure}}
{| class="toccolours" style="float: right; margin: 0 0 1em 1em; border:none; font-size: 95%; clear: right; padding:0"
|+ An example of visualizing pawn structures
|-
|{{Chess diagram small
|
|
|rd|__|bd|__|rd|__|kd|__
|pd|pd|__|nd|__|pd|bd|pd
|__|__|pd|rl|__|nd|pd|__
|__|__|__|__|pd|__|__|__
|__|__|pl|__|pl|__|__|__
|__|__|nl|__|bl|nl|__|pl
|pl|pl|__|__|__|pl|pl|__
|__|__|kl|__|__|bl|__|rl
| After 12...Re8 in Tarrasch–Euwe, 1922<ref>{{cite web |url = http://www.chessgames.com/perl/chessgame?gid=1006866 |title = Tarrasch vs Euwe on chessgames.com}} (Java needed)</ref> ...
}}
| {{Chess diagram small
|
|
|__|__|__|__|__|__|__|__
|pd|pd|__|__|__|pd|__|pd
|__|__|pd|__|__|__|pd|__
|__|__|__|__|pd|__|__|__
|__|__|pl|__|pl|__|__|__
|__|__|__|__|__|__|__|pl
|pl|pl|__|__|__|pl|pl|__
|__|__|__|__|__|__|__|__
| ... and its pawn skeleton ("The Rauzer formation")
}}
|}
In the endgame, [[passed pawn]]s, unhindered by enemy pawns from [[Promotion (chess)|promotion]], are strong, especially if advanced or protected by another pawn. A passed pawn on the sixth {{chessgloss|rank}} is roughly as strong as a knight or bishop and often decides the game. (Also see [[isolated pawn]], [[doubled pawns]], [[backward pawn]], [[connected pawns]].)

==== Knights ====
{{Main|Knight (chess)|l1=Knight}}
Since knights can easily be chased away by pawn moves, it is often advantageous for knights to be placed in ''{{chessgloss|holes}}'' in the enemy position as [[Outpost (chess)|outposts]]—squares where they cannot be attacked by pawns. Such a knight on the fifth rank is a strong asset. The ideal position for a knight is the opponent's third rank, when it is supported by one or two pawns.<ref>{{cite web|url=http://www.thechessdrum.net/chessacademy/CA_TheKnight.html|title=The Knight|website=www.thechessdrum.net|access-date=3 April 2018}}</ref> A knight at the edge or corner of the board controls fewer squares than one on the board's interior, thus the saying "A knight on the rim is dim!"

A king and one knight are not sufficient material to [[checkmate]] an opposing [[lone king]] (see [[Two knights endgame]]). A king and two knights can checkmate a lone king but cannot force it.

==== Bishops ====
{{Main|Bishop (chess)|l1=Bishop}}
In general, bishops and knights are of roughly equal value. When bishops are blocked in by pawns, as seen in closed positions, knights are typically superior for their ability to hop over pawn chains. In open positions where bishops have good {{chessgloss|scope}}, knights are often inferior—{{chessgloss|outpost}} knights are a common exception.

Bishops have superior mobility to knights, but that mobility is restricted to (and thus focused on) colors of a single square. As a result, lacking a bishop weakens one's ability to exert control over and parry threats from the deprived color complex, though there may be compensation in the form of tactical or positional assets, or from possible countermeasures, such as placing one's pawns on the color of the lost bishop. Bishops complement each other well, and a retained {{chessgloss|bishop pair}} is often a strength, especially in open positions.

''[[Fianchetto]]ed'' bishops can keep a king under them well defended, though if the bishop is traded off, the fianchetto pawn structure is especially vulnerable to infiltration on the squares no longer controlled by the bishop.

Despite their openness, in endgames, bishops are usually considered equal to knights. Endgames in which the two sides have [[Opposite-colored bishops endgame|bishops on opposite colors]] are frequently drawish, even when one side has one or two more pawns than the other.

A king and a bishop are not sufficient material to checkmate an opposing lone king, but two bishops and a king can checkmate an opposing lone king easily. A [[Bishop and knight mate|king, bishop, and knight]] can also force mate; this is considered the most difficult forcible checkmate against a lone king.

==== Rooks ====
{{Main|Rook (chess)|l1=Rook}}
Rooks have more scope of movement on [[half-open file]]s (ones with no pawns of one's own color). Rooks on the seventh rank can be very powerful as they attack pawns that can only be defended by other pieces, and they can restrict the enemy king to its back rank. A pair of rooks on the player's seventh rank are often a sign of a winning position.

In [[Chess middlegame|middlegames]] and [[Chess endgame|endgames]] with a passed pawn, [[Tarrasch rule|Tarrasch's rule]] states that rooks, both friend and foe of the pawn, are usually strongest {{em|behind}} the pawn rather than in front of it.

A king and a rook are sufficient material to checkmate an opposing lone king, although it's a little harder than checkmating with king and queen; thus the rook's distinction as a major piece above the knight and bishop.

==== Queen ====
{{Main|Queen (chess)|l1=Queen}}

Queens are the most powerful pieces. They have great mobility and can make many threats at once. They can act as a rook and as a bishop at the same time. For these reasons, [[checkmate]] attacks involving a queen are easier to achieve than those without one. Although powerful, the queen is also easily harassed. Thus, it is generally wise to wait to {{chessgloss|develop}} the queen until after the knights and bishops have been developed to prevent the queen from being attacked by minor pieces and losing [[tempo (chess)|tempo]]. When a [[Pawn promotion|pawn is promoted]], most of the time it is promoted to a queen.

==== King ====
{{Main|King (chess)|l1=King}}
During the middlegame, the king is often best protected in a corner behind its pawns. Such a position for either of the players is often achieved by [[castling]] by that player. If the rooks and queen leave the first rank (commonly called that player's ''back rank''), however, an enemy rook or queen can checkmate the king by invading the first rank, commonly called a [[back-rank checkmate]]. Moving one of the pawns in front of the king (making a [[luft]]) can allow it an escape square, but may weaken the king's overall safety otherwise. One must therefore wisely balance between these trade-offs.

Castling is often thought to help protect the king and often "connects" the player's two rooks together so the two rooks may protect each other. This can reduce a threat of a back-rank [[Skewer (chess)|skewer]] in which the king can be skewered with capture of a rook behind it.

The king can become a strong piece in the endgame. With reduced material, a quick checkmate becomes less of a concern, and moving the king towards the center of the board gives it more opportunities to make threats and actively influence play.