The BDS Website

BDS

Paisley, 1996

#2
LEO h3
PAOs h2; d3, d7
VAOs a2, g5; b4, g1, h7
MAOs b3, d4

1.VAf4! (2.Ba7#)

1...MAf3 2.Sxd7# (2.Sxd3?)
1...MAe6 2.Sxd3# (2.Sxd7?)
1...MAf5 2.PAc2#
1...PAb7 2.Sxd3#

After the key, any move by the black MAO on d4 defends against the threat. If it were to disappear from the board completely then, because of its removal as a hurdle between the two black PAOs, over which they defend each other, both mates 2.Sxd7 and 2.Sxd3 would be possible. But it has to land somewhere and its arrival on f3 or e6 provides a hurdle over which one of d7 or d3 is newly guarded, so allowing only one of those mates. This is a Chinese form of the Herpai dual-avoidance theme. The third variation 1...MAf5, also by that black MAO, guards both d7 and d3, but allows 2.PAc2#.

This matrix took a good ten years to get into a publishable form. Even now though, the use of three black VAOs is a flaw that I would like to eliminate.