The BDS Website

BDS, Jörg Kuhlmann & John Rice

#2
Isardam

1.Qg6!  (2.Qd6#)

1...Rxe5 2.Qc6#
1...Qxe5 2.Rc5#
1...Be6  2.c4#
1...e6   2.Bc4#

After the key, the wQ can't be captured by 1...fxg6 as that move is illegal because after it two pawns of opposite colour would observe each other. The threat can’t be nullified for similar reasons. Black’s first two defences capture on e5 so that Black can legally reply to the threat by 2...exd6. 1...Rxe5 allows 2.Qc6# because Black cannot then play 2...Qxe5. If he could, 2.Qc6 would not be mate because the threat of capturing the black king would disappear. After 1...Qxe5 Black cannot play 2...Rxe5 and this allows 2.Rc5# for similar reasons. Black’s next two defences block White’s access to d6 by occupying e6, but also stop other black units from getting to e6. 1...Be6 allows 2.c4# as Black can't now play 2...e6 and 1...e6 lets in 2.Bc4# because 2...Be6 is then impossible. Two pairs of black mutual obstructions.

Another example of co-operation at a meeting of problemists. Jörg and I had been struggling getting our idea sound, but were rescued just before the tourney deadline by John Rice.