Fairy chess composition
 No.1329  Andreas Thoma (Germany) Original Fairy problems JF-2018/II: July – December’2018

Definition: (click to show/hide)

 No.1329 Andreas Thoma Germany original – 30.09.2018 dedicated to Christian Poisson Solutions: (click to show/hide) white Kd4e6 Sd6 Bg6 Pd5 black Qd8 Bf8 Rh6 ser-#3         b) Sd6→d5             (5+3) Wandelschach a) 1.Kd4-c5 2.Kc5-c6 3.Sd6-e8=bK # b) wSd6-->d5 1.Kd4-e5 2.Sd5-f6 3.Bg6-e8=bK # { (C+ by WinChloe 3.42, "Changeants" condition)} To take the B(S) is illegal, because the wK cannot escape the check (both wK’s must be mated. (Author)

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dupont
October 1, 2018 12:22

Sorry but I don’t understand why solution a) ends in a checkmate position. After Rh6xBg6 the bK is no more in-check, so why isn’t it a valid defense?

François Labelle
October 1, 2018 17:29

The fairy definition given here doesn’t say how multiple kings are handled (Rex Multiplex? Royal Dynasty? Siamese Kings?). The definition given in https://juliasfairies.com/problems/jf-2016-i/no-1037/ says that it is Rex Multiplex. In Rex Multiplex, Rh6xBg6 isn’t legal because it delivers a check which can’t be parried, but it doesn’t mate both kings.

seetharaman
October 1, 2018 18:30

Is the twin right?

Stephen Emmerson
October 1, 2018 21:38

Something is wrong with the animation, clicking on “b)” does not show the twin position.

dupont
October 1, 2018 18:36

The link says more precisely that Rex Multiplex applies when a second King of same color appears during the solution…

I wasn’t aware of that kind of illegal move in RM. It looks debatable, in fact I don’t understand why Rh6xBg6 should be a check, as the black side doesn’t threat to capture both wKs!

October 1, 2018 21:29

There are various possibilities for treatment of multiple kings, as Francois rightly points. Actually three of them mentioned by him lead to different verdicts about 3…Rxg6:
– Rex Multiples allows only checks that either can be parried without any king left in check or checkmate all kings. In Rex Multiples 3…Rxg6 is illegal as it checks Ke6, but White is unable to parry it without leaving some its kings under check.
– Siamese Kings allows any check and consider as checkmates checks that cannot be parried in a manner leaving all kings unchecked. In Siamese Kings 3…Rxg6 would checkmate White.
– Royal Dynasty considers as check only attack at the last Kings standing, thus 3…Rxg6 would parry the check to Black and even did not check White.

Geoff Foster
October 2, 2018 00:58

The twin has a double-check mate and the logic is different. After 3…Rxf6+ the checked white King could escape with 4.Kd5. However 3…Rxf6+ is illegal because the black King is still in check from the wSd6.

Joost
October 3, 2018 07:59

Geoff, the check isn’t a double check. Sd6 isn’t there, because the twin building of the diagram was wrong.

Geoff Foster
October 4, 2018 00:46