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| (1) Posted by Hauke Reddmann [Sunday, Jul 16, 2023 15:53] |
Nietvelt vs Schiffmann
How do you call a Black 2# self-pin which actually defends?
Or the mate doesn't use the pin?
Is Nietvelt parade (direct) resp. Schiffmann parade (indirect)
accepted use?
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| (2) Posted by Viktor Syzonenko [Sunday, Jul 16, 2023 22:44] |
Nietvelt and Schiffmann Co
The aim of self-pin: to be untied when trying to implement a threat.
If the variant does not use this self-pin, then there is no paradox. And the value of such defence is plummeting.
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| (3) Posted by Neal Turner [Monday, Jul 17, 2023 19:28] |
There's also the Drese Theme:
Black self-pins his piece in anticipation that White unpins it. White does that, but in another way than Black was prepared for.
Gerardus H. DRESE
Jaarboek 1935
 (= 9+5 )
#3
1.Bf5! ~ 2.Bc8 ~ 3.Ba6#;
1... S2xe4 2.Bh3! (2.Bc8? Sxc5!) ~ 3.Bf1#, 2... Sxc3(Sg3) 3.Re3#, 2... Sxd2 3.Sc1#;
1... S6xe4 2.Bd7! (2.Bc8? Sxc5!) ~ 3.Bb5#, 2... Sxc3/Sd6 3.Re3#, 2... Sxd2 3.Sc1#;
(1... S6g4/S2g4/etc. 2.exd5+ Se4 3.Bxe4#)
A 3-move scheme, but also maybe possible with a s#2.
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| (4) Posted by Hauke Reddmann [Monday, Jul 17, 2023 21:21] |
 (= 7+4 )
Offhand I don't see why Drese should be impossible even in #2:
threat 2.g5, 1...Rxf6 2.g5? 2.De1#!
(To state the obvious, that's not even a matrix :-)
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| (5) Posted by Kevin Begley [Tuesday, Jul 18, 2023 03:09] |
Is a unit unpinned after checkmate?
Maybe, technically, but mate kills the paradox.
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| (6) Posted by Neal Turner [Tuesday, Jul 18, 2023 07:16] |
Not even technically.
Pins/unpins are not static, but dynamic features.
With a pin there must be some line that succeeds only because of the constraints on the pinned piece, while the actual or possible moves of an unpinned piece must be affecting the play - either before or after the unpin.
Without this, the terms have no meaning.
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| (7) Posted by Sarah Hornecker [Tuesday, Jul 18, 2023 09:22] |
So if we disregard (remove) the threat, Hauke's example would be better if it was more like:
 (= 7+4 )
1.-Rxf6 2.Qe4+? Rf4!, 2.Qe1#!
With a fairy piece and minor changes, his example or my variation thereof would be easy to construct into a real #2.
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| (8) Posted by Hauke Reddmann [Tuesday, Jul 18, 2023 09:41] |
I see no difference in the two sketches (except for direct vs indirect unpin).
Clearly, the unpinned piece can't play any role in the mate
(or White couldn't have unpinned it at all) but only in
the refusal of the threat. And clearly, as Neal and
Victor already pointed out, this is a shortcoming of
a 2# Drese (or any self-pin that isn't used at all).
(My strictly terminological question still waits :-)
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| (9) Posted by Hauke Reddmann [Tuesday, Jul 18, 2023 11:21] |
Look, Sarah, no fairy pieces :-)
 (= 6+8 )
1.Dxe3! (2.Dxe1#) Txf3 2.Dg5# (2.Dxe1??; 2.Sxf5 - if that would be
legal - would be a normal Nietvelt self-pin exploit)
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