A pure mate is a checkmating

Checkmate

Checkmate is a situation in chess in which one player's king is threatened with capture and there is no way to meet that threat. Or, simply put, the king is under direct attack and cannot avoid being captured...

 position in chess

Chess

Chess is a two-player board game played on a chessboard, a square-checkered board with 64 squares arranged in an eight-by-eight grid. It is one of the world's most popular games, played by millions of people worldwide at home, in clubs, online, by correspondence, and in tournaments.Each player...

 in which the mated king and all vacant squares in its field are attacked only once, and squares in the king's

King (chess)

In chess, the king is the most important piece. The object of the game is to trap the opponent's king so that its escape is not possible . If a player's king is threatened with capture, it is said to be in check, and the player must remove the threat of capture on the next move. If this cannot be...

 field occupied by friendly units are not also attacked by the mating side (unless such a unit is necessarily pin

Pin (chess)

In chess, a pin is a situation brought on by an attacking piece in which a defending piece cannot move without exposing a more valuable defending piece on its other side to capture by the attacking piece...

ned to the king to avoid it interposing to block the check or capturing of mating unit).

Such a mate occurred in the Evergreen Game

Evergreen game

The Evergreen game is a famous chess game played in Berlin in 1852 between Adolf Anderssen and Jean Dufresne.Adolf Anderssen was one of the strongest players of his time, and was considered by many to be the world champion after winning the London 1851 tournament. Jean Dufresne, a popular author of...

 between Adolf Anderssen

Adolf Anderssen

Karl Ernst Adolf Anderssen was a German chess master. He is considered to have been the world's leading chess player in the 1850s and 1860s...

 and Jean Dufresne

Jean Dufresne

Jean Dufresne was a German chess player and chess composer. He was a student of Adolf Anderssen, and lost the "Evergreen game" to him in 1852. Dufresne was an unsuccessful novelist under the anagrammatic pseudonym E. S...

 in 1852; the final position is shown to the right. The black king is attacked only by the bishop on e7; the e7 and g7 squares are attacked only by the pawn on f6; the e8 square is attacked only by the bishop on d7; and the rook on g8 and pawn on f7 which stop the black king moving to those squares are not also attacked by white pieces.

Pure mates are of only incidental interest in practical play, but they are considered by some to add value to a chess problem

Chess problem

A chess problem, also called a chess composition, is a puzzle set by somebody using chess pieces on a chess board, that presents the solver with a particular task to be achieved. For instance, a position might be given with the instruction that White is to move first, and checkmate Black in two...

.

If all units of the mating side, with the possible exception of the king and pawns, are involved in a pure mate, then it is a model mate

Model mate

A model mate is a type of pure mate checkmating position in chess in which not only is the checkmated king and all vacant squares in its field attacked only once, and squares in the king's field occupied by friendly units are not also attacked by the mating side , but all units of the mating side A...

; if all units of both colours are involved in a pure mate, then it is an ideal mate

Ideal mate

In chess, an ideal mate is a checkmate position that is a special form of model mate. While in a model mate, each piece on the mating player's side participates in the mate, an ideal mate involves all the pieces of the mated player's as well, typically by blocking the mated king's field of...

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