Space

Other things being equal, the side that controls more space on the board has an advantage.^[2] 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 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.

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

White has an advantage in space.^[3]

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.^[3]

Control of the center

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

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. 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.

Initiative

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.^[4] 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 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 back rank. These situations can easily occur if the pawn structure is weak.

Exchanging pieces

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]}

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" 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 articles: Pawn and Pawn structure

An example of visualizing pawn structures

a b c d e f g h 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 a b c d e f g h After 12...Re8 in Tarrasch–Euwe, 1922[5] ...

a b c d e f g h 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 a b c d e f g h ... and its pawn skeleton ("The Rauzer formation")

In the endgame, passed pawns, unhindered by enemy pawns from promotion, are strong, especially if advanced or protected by another pawn. A passed pawn on the sixth 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.)

Opening

A chess opening is the group of initial moves of a game (the "opening moves"). Recognized sequences of opening moves are referred to as openings and have been given names such as the Ruy Lopez or Sicilian Defence. They are catalogued in reference works such as the Encyclopaedia of Chess Openings. It is recommended for anyone but the chessmasters that when left with a choice to either invent a new variation or follow a standard opening, choose the latter.^{[citation needed]}

There are dozens of different openings, varying widely in character from quiet positional play (e.g. the Réti Opening) to very aggressive play (e.g. the Latvian Gambit). In some opening lines, the exact sequence considered best for both sides has been worked out to 30–35 moves or more.^[7] Professional players spend years studying openings, and continue doing so throughout their careers, as opening theory continues to evolve.

The fundamental strategic aims of most openings are similar:^[8]

• Development: To place (develop) the pieces (particularly bishops and knights) on useful squares where they influence the game.
• Control of the center: Control of the central squares allows pieces to be moved to any part of the board relatively easily, and can also have a cramping effect on the opponent.
• King safety: Correct timing of castling can enhance this.
• Pawn structure: Players strive to avoid the creation of pawn weaknesses such as isolated, doubled or backward pawns, and pawn islands.

During the opening, some pieces have a recognized optimum square they try to reach. Hence, an optimum deployment could be to push the king and queen pawn two squares, followed by moving the knights so they protect the center pawns and give additional control of the center. One can then deploy the bishops, protected by the knights, to pin the opponent's knights and pawns. An opening may end with castling, which moves the king to safety, creates a stronger back rank, and puts a rook on a center file.

Apart from these fundamentals, other strategic plans or tactical sequences may be employed in the opening.

Most players and theoreticians consider that White, by virtue of the first move, begins the game with a small advantage. Black usually strives to neutralize White's advantage and achieve equality, or to develop dynamic counterplay in an unbalanced position.

Middlegame

The middlegame is the part of the game when most pieces have been developed. Because the opening theory has ended, players have to assess the position to form plans based on the features of the positions, and at the same time take into account the tactical possibilities in the position.^[9]

Typical plans or strategic themes—for example the minority attack, that is the attack of queenside pawns against an opponent who has more pawns on the queenside—are often appropriate just for some pawn structures, resulting from a specific group of openings. The study of openings should therefore be connected with the preparation of plans typical for resulting middlegames.

The middlegame is also the phase when most combinations occur.^[10] Middlegame combinations are often connected with the attack against the opponent's king; some typical patterns have their own names, for example the Boden's Mate or the Lasker–Bauer combination.

Another important strategical question in the middlegame is whether and how to reduce material and transform into an endgame (i.e. simplify). For example, minor material advantages can generally be transformed into victory only in an endgame, and therefore the stronger side must choose an appropriate way to achieve an ending. Not every reduction of material is good for this purpose; for example, if one side keeps a light-squared bishop and the opponent has a dark-squared one, the transformation into a bishops and pawns ending is usually advantageous for the weaker side only, because an endgame with bishops on opposite colors is likely to be a draw, even with an advantage of one or two pawns.

Endgame

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

An example of zugzwang: The side to move has a disadvantage.

The endgame (or end game or ending) is the stage of the game when there are few pieces left on the board. There are three main strategic differences between earlier stages of the game and the endgame:^[11]

• During the endgame, pawns become more important; endgames often revolve around attempting to promote a pawn by advancing it to the eighth rank.
• The king, which must be protected in the middlegame owing to the threat of checkmate, becomes a strong piece in the endgame and it is often brought to the center of the board where it can protect its own pawns, attack the pawns of opposite color, and hinder movement of the opponent's king.
• Zugzwang, a disadvantage because the player must make a move, is often a factor in endgames and rarely in other stages of the game. For example, in the adjacent diagram, Black on move must play 1...Kb7 and allow white to queen after 2.Kd7, while White on move must allow a draw either after 1.Kc6 stalemate or losing the last pawn by moving anywhere else.

Endgames can be classified according to the type of pieces remaining on the board. Basic checkmates are positions where one side has only a king and the other side has one or two pieces and can checkmate the opposing king, with the pieces working together with their king. For example, king and pawn endgames involve only kings and pawns on one or both sides and the task of the stronger side is to promote one of the pawns. Other more complicated endings are classified according to the pieces on the board other than kings, e.g. "rook and pawn versus rook endgame".