Problem 1023: James Quah - Fairy (Patrol Chess, Rose, Nightrider)

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Problem 1023: James Quah - Fairy (Patrol Chess, Rose, Nightrider)

(31.12.2019) Another interesting fairy original by James Quah.

The royal battery behaves as though the king “shuts off” the defences
2…Bxd4/Nxd3. In contrast, the rook interference is an ordinary double interference
for which we need 2.Bxb4, but Nb2 is not involved.

It would be nice to have all defenders attacking the same source of the mate, and on
each occasion, one defender shuts off all others, then finds itself shut off when white
mates. With a rose, we have two routes to the same square, and two different firing
units, which shut off black units in a different way.

1023. James Quah (Singapure)

#2 Patrol Chess (13+11)

b7,d7,h2: Nightrider

b1,b3,c7,h2: Rose

Defences against ROb3-a5-b7-d8-f7-g5: Rxb3/Nxd7/Bb7/ROf7
Defences against ROb3-c5-e6-f5: Bxd5/ROxf7

1.Sg6! (2.f4#)
1…Rf3 2.Nd3#
1…Nf3 2.bNc5#
1…Bf3 2.Kf7#
1…ROf3 2.Kd5#
1…Rxg4 2.Rh5#

The key takes two flights, one of which is unprovided, but the alternative Nowotny
setting with key 1.f3! with 4 threats is unattractive.
Patrol chess is needed otherwise the matrix would not even be possible.
1…Bd5+/Na4+ would spoil it, as would 1.Ne1 double check. It also enables 1…Nf3 2.bNc5.