The BDS Website

BDS

British Chess Magazine, 1978

#2
GRASSHOPPERs b4, c7, e6, g2
NIGHTRIDER f3

1.Nxg5!  (2.fxe6#)

1...Ge~   2.Rxc7#
1...Gg4!  2.Rd4#
1...Ge4!! 2.e6#

After the key, all defences are by the bGe6. A random move uncovers the guard on c7 from the wNg5, leading to 2.Rxc7#. Black can correct this error by pinning the wRc4. Thus 1...Gg4! But this makes the further error of interfering with the bRh4, so allowing 2.Rd4#. Black can further correct against this error by playing 1...Ge4!!, allowing 2...Gd5! after the putative 2.Rd4+. But this moves makes a further error, that of 'guarding' its departure square over a white pawn that can mate by moving onto that departure square. Such a mechanism is called Black Tertiary Correction. I had never seen it done with a Grasshopper, so set out to do it. This theme was not pointed out on publication and nobody appeared to notice it. One bemused solver commented (and I paraphrase), "What was all that about?" Some chess problem themes can be esoteric, especially when done with fairy pieces and/or fairy conditions. But, believe me, this example is elementary compared to what the leading fairy composers are doing these days!