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The Problemist, 1993

#2
Symmetric Circe

1.Qc2!         (2.Qxa4#)

1...Sf4         2.Bxc5#
1...Sg3         2.Rxb6#
1...Sf6         2.Qxc3#
1...dxc2(+wQf7) 2.Qxc4#
1...Rb5         2.Sc6#

By playing 1.Qc2, White is threatening to mate by capturing the rook on a4, which, with h5 occupied, would leave the board. However, if h5 were not occupied, that threat would be illegal as the black rook would be reborn on h5, from where it would check the white king. Black defends by moving his knight, but wherever it lands it blocks a square from which a reborn black piece would otherwise check the white king if it were propelled there by White via capture. Thus the defence motivation and the error of these knight variations are two sides of the same coin. The defence by the black d-pawn merely moves the white queen to a square from which it can mate on a different square and the last variation has nothing unorthodox about it at all.