[Retros] shortest proofgames of castling switchback

Noam Elkies elkies at math.harvard.edu
Tue Jul 17 13:45:24 EDT 2007


"Mario Richter" <mri_two at t-online.de> writes:


> [NDE wrote:]



> | in 20.5 (switchback is completed after 19.5):

> | 1 g3 a5 2 Bg2 Ra6 3 Be4 Rf6 4 Nf3 d6 5 0-0 Qd7 6 Kh1 Qh3

> | 7 Rg1 Qf1 8 b3 Bh3 9 Ba3 Rf5 10 Qc1 f6 11 Qb2 Kf7 12 Qd4 Kg6

> | 13 Nc3 Qb1 14 Bc1 Kh5 15 Rg2 g6 16 Kg1 Bh6 17 Kf1 Bg5 18 Ke1 Nh6

> | 19 Rg1 Rf8 20 Rh1 Ng8 21 Ng1

> |

> | . n . . . r n . hg-20.5

> | . p p . p . . p

> | . . . p . p p .

> | p . . . . r b k

> | . . . Q B . . .

> | . P N . . . P b

> | P . P P P P . P

> | R q B . K . N R 16+16

> |

> | NDE 17.vii.2007

> |

> | ... Does this work?



> Maybe you should put the black rook Rf8 on e8 instead,

> otherwise the following cook is possible: [...]


Indeed I had neglected to check Black's 0-0 options...
Yes, please change 19...Rf8 to 19...Re8, thanks.

Meanwhile I have a potential fix for the 19-move attempt at a
White castling switchback in a captureless sound helpgame:
change the sequence 12 Re3 Qf3 13 Bh2 Qh3 14 g3 to
12 Rg3 Qf3 13 Rg5 Qh5 14 g4, giving this diagram:

r Q B . k . . r hg-19.0
p . p p p p . p
n p . . . n p R
. b . . b . R q
P . . . . B P P
. P . P . . . .
. . P . P P . .
. N . . K . N . 16+16

NDE 17.vii.2007

--Noam D. Elkies



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