Editing Pure mate (section)

{{Short description|Special checkmate position}}

{{Chess diagram
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| {{big|'''Pure mate'''}}
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| A [[chess problem|composed]] example of a pure mate.<ref name="Beasley">{{cite web |last=Pospíšil |first=Josef |title=An Outline of The Theory of Chess Problems |year=1999 |orig-date=Originally published in 1887 |translator-last=Beasley |translator-first=John |url=https://www.jsbeasley.co.uk/ochess/posp.pdf |page=8}}</ref> The black king is attacked once.  Every square surrounding the king is covered exactly once: c6 and d6 are attacked by the white king, e6 is attacked by the white bishop, e5 and d4 are attacked by the white knight, and e4 and c5 are each blocked by black units which are not also attacked by white units.  c4 is {{em|guarded}} by the white bishop.
}}

In [[chess]], a '''pure mate''' is a [[checkmate]] position such that the mated [[King (chess)|king]] is attacked exactly once, and prevented from moving to any of the adjacent squares in its {{chessprobgloss|king's field|field}} for exactly one reason per square.<ref name="Maizelis">{{cite book |last=Maizelis |first=Ilya |author-link=Ilya Maizelis |title=The Soviet Chess Primer |date=7 March 2015 |publisher=[[Quality Chess]] |isbn=9781907982996 |page=377}}</ref> Each of the squares in the mated king's field is attacked or "guarded" by one—and only one—attacking unit, or else a square which is not attacked is occupied by a friendly unit, a unit of the same color as the mated king. Some authors allow that special situations involving [[double check]] or [[Pin (chess)|pins]] may also be considered as pure mate.

Pure mates are of interest to [[chess problem]] [[Chess composer|composers]] for their [[Chess aesthetics|aesthetic]] value. In real gameplay, their occurrence is incidental. Nevertheless, several famous games have concluded with a pure mate, including the [[Immortal Game]] and the [[Evergreen Game]], both won by [[Adolf Anderssen]]; the [[Peruvian Immortal]]; and the [[Game of the Century (chess)|Game of the Century]], an early {{chessgloss|brilliancy}} won by [[Bobby Fischer]].

Pure mate is one of a few terms used by composers to describe the properties of a checkmate position; related concepts include [[economical mate]], [[model mate]], and [[ideal mate]]. An economical mate is a position such that all of the attacker's [[Chess piece#Usage of the term piece|pieces]]{{efn|In chess literature, the word ''piece'' is commonly used to refer to the more powerful units, all units other than the pawns.  In some contexts, however, it may refer to all material on the board, including the pawns.}} contribute to the checkmate, with the (optional) exception of the king and the pawns.{{sfn|Horton|p=56}}{{efn|In an economical mate, the king and pawns may play a role in the checkmate, but it is not required.}} The model mate and the ideal mate are both stronger forms of pure mate. When a checkmate is both "pure and economical", it is said to be a model mate.<ref name="Maizelis" />{{sfn|Hooper & Whyld|p=262}}{{sfn|Horton|pp=133-134}} When, in a pure mate, all {{chessgloss|material}} on the board of either color plays a direct role in the checkmate, it is said to be an ideal mate.{{sfn|Hooper & Whyld|p=179}}
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