Pure mate

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Anderssen-Dufresne, 1852
a b c d e f g h
b8 black rook
f8 black king
g8 black rook
a7 black pawn
b7 black bishop
c7 black pawn
d7 white bishop
e7 white bishop
f7 black pawn
h7 black pawn
b6 black bishop
f6 white pawn
c3 white pawn
f3 black queen
a2 white pawn
f2 white pawn
g2 white pawn
h2 white pawn
d1 white rook
g1 white king
7 7
6 6
5 5
4 4
3 3
2 2
1 1
a b c d e f g h
Final position

A pure mate is a checkmating position in chess in which the mated king and all vacant squares in its field are attacked only once, and squares in the king's field occupied by friendly units are not also attacked by the mating side (unless such a unit is necessarily pinned to the king to avoid it interposing to block the check or capturing of mating unit).

Such a mate occurred in the Evergreen Game between Adolf Anderssen and Jean Dufresne 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.

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