Editing Chess (section)

===Phases===
Chess theory divides chess games into three phases with different sets of strategies: the [[#Opening|opening]], the [[#Middlegame|middlegame]], and lastly the [[#Endgame|endgame]]. There is no universally accepted way to delineate the three phases of the game; the middlegame is typically considered to have begun after 10–20 moves, and the endgame when only a few pieces remain.

====Opening====
{{Main|Chess opening}}
{{Chess diagram  
|tright
|
|rd|nd|bd|qd|kd|bd|  |rd
|  |pd|  |  |pd|pd|pd|pd
|pd|  |  |pd|  |nd|  |  
|  |  |  |  |  |  |  |  
|  |  |  |nl|pl|  |  |  
|  |  |nl|  |  |  |  |  
|pl|pl|pl|  |  |pl|pl|pl
|rl|  |bl|ql|kl|bl|  |rl
|The [[Sicilian Defense, Najdorf Variation|Najdorf Variation]] (5...a6), a popular line of the [[Sicilian Defense]] (1...c5), itself a response to the [[King's Pawn Game]] (1.e4)
}}
Competitive players typically learn, memorize, and play well-documented sequences of opening moves. The most common starting moves for White are '''1.e4''' and '''1.d4''', which usually lead to substantially different types of positions, and Black has multiple viable responses to both.

Sequences of opening moves are referred to as ''openings'' and are catalogued in reference works, such as the ''[[Encyclopaedia of Chess Openings]]''. There are thousands of openings, though only a small fraction of them are commonly played; variations of openings may also be given names. Openings vary widely in character from quiet {{chessgloss|positional play}} (for example, the [[Réti Opening]]) to {{chessgloss|sharp}} aggressive play (like the [[Latvian Gambit]]). In some opening lines, the exact sequence considered best for both sides has been worked out to more than 30 moves.<ref>{{harvp|Tamburro|2010|p=18}}</ref>

The fundamental strategic aims of most openings are similar:<ref>{{harvp|Tarrasch|1987}}</ref>
* ''Development:'' moving pieces (particularly bishops and knights) forward to squares on which they are useful (defending, attacking, and controlling important squares) and/or have the potential to take part in future plans and ideas.
* ''Control of the {{chessgloss|center}}:'' control of the central squares allows pieces to be moved to any part of the board relatively easily, and can inhibit the mobility of the opponent's pieces.
* ''King safety:'' typically secured by castling; incorrectly timed castling can be wasteful or even harmful, however.
* ''[[Pawn structure]]:'' players strive to avoid the creation of pawn weaknesses such as isolated, doubled, or backward pawns&nbsp;– and to force such weaknesses in the opponent's position.

Most players and [[Chess theory|theoreticians]] consider that White, by virtue of the [[Initiative (chess)|initiative]] granted from moving first, [[First-move advantage in chess|begins the game with a small advantage]].<ref>{{harvp|Evans|1958|p=175}}</ref> Black usually strives to neutralize White's advantage and achieve {{chessgloss|equality}}, or to develop {{chessgloss|dynamic}} {{chessgloss|counterplay}} in an unbalanced position.

====Middlegame====
{{Main|Chess middlegame}}
The middlegame is the part of the game that starts after the opening. Because the opening theory has ended, players have to form plans based on the features of the position, and at the same time take into account the tactical possibilities of the position.<ref>{{harvp|Harding|2003|pp=32–151}}</ref> The middlegame is the phase in which most [[Combination (chess)|combinations]] occur. Combinations are a series of tactical moves executed to achieve some gain. Middlegame combinations are often connected with an attack against the opponent's king. Some typical patterns have their own names; for example, the [[Boden's Mate]] or the [[Lasker - Bauer, Amsterdam, 1889|Lasker–Bauer]] combination.<ref>{{harvp|Hooper|Whyld|1992|p=86}}</ref>

Specific plans or strategic themes will often arise from particular groups of openings that result in a specific type of pawn structure. An example is the {{chessgloss|minority attack}}, which is the attack of queenside pawns against an opponent who has more pawns on the queenside. The study of openings is therefore connected to the preparation of plans that are typical of the resulting middlegames.<ref>{{harvp|Silman|1998|pp=202–205}}</ref>

Another important strategic question in the middlegame is whether and how to reduce material and transition into an endgame (i.e. {{chessgloss|simplify}}). 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 [[Chess endgame#Bishop and pawn endings|bishops and pawns]] ending is usually advantageous for the weaker side only, because an endgame with [[opposite-colored bishops endgame|bishops on opposite colors]] is likely to be a draw, even with an advantage of a pawn, or sometimes even with a two-pawn advantage.<ref>{{harvp|Emms|2004|p=90}}</ref>

====Endgame====
{{Main|Chess endgame}}
{{Chess diagram  
|tright
|Example of zugzwang
|  |  |kd|  |  |  |  | 
|  |  |pl|  |  |  |  | 
|  |  |  |kl|  |  |  | 
|  |  |  |  |  |  |  | 
|  |  |  |  |  |  |  | 
|  |  |  |  |  |  |  | 
|  |  |  |  |  |  |  | 
|  |  |  |  |  |  |  | 
|The side to move is disadvantaged.
}}

The endgame (also ''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:<ref>{{harvp|Harding|2003|pp=187ff}}</ref>
* Pawns become more important. Endgames often revolve around endeavors to [[Promotion (chess)|promote]] a pawn by advancing it to the furthest {{chessgloss|rank}}.
* The king, which requires safeguarding from attack during the middlegame, emerges as a strong piece in the endgame. It is often used to protect its own pawns, attack enemy pawns, and hinder moves of the opponent's king.
* [[Zugzwang]], a situation in which the player who is to move is forced to incur a disadvantage, is often a factor in endgames but rarely in other stages of the game. In the example diagram, either side having the move is in zugzwang: Black to move must play 1...Kb7 allowing White to promote the pawn after 2.Kd7; White to move must permit a draw, either by 1.Kc6 [[stalemate]] or by losing the pawn after any other legal move.

Endgames can be classified according to the type of pieces remaining on the board. [[Checkmate#Basic checkmates|Basic checkmates]] are positions in which 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 endgame]]s 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 pieces on the board other than kings, such as "[[rook and pawn versus rook]]" endgames.
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