[Retros] Illegal moves by grandmasters

A J Mestel A.J.Mestel at damtp.cam.ac.uk
Thu May 12 09:12:57 EDT 2011

Most of what I say is tangential. I suppose that means I'm not

On Wed, 11 May 2011, Noam Elkies wrote:

> A J Mestel <A.J.Mestel at damtp.cam.ac.uk> writes:


>> Yes...and Noam has quite a nice study based on the 50move rule, which

>> he'll doubtless share with us, if someone jogs his memory...J


> Thanks; and yes, I remember the study, though it feels only tangentially

> related to the issue here, and I freely admit that it's a joke study:

> the main point -- move order determined by 50-move deadline in the

> future -- is invalid according to both Codex (it's not a retro study)

> and common sense of sufficiently expert solvers (corroborated by

> anecdotal evidence that, in some range of expertise, success with

> this study is negatively correlated with chess ability).


> Probably most everybody on this forum has seen that position already

> (e.g. <http://www.chessbase.com/puzzle/christmas2009/chr09-08.htm>);

> it's probably my best known chess study, illegitimate though it be

> -- the joke was apparently an effective one. So I'll note only a

> point that's sometimes missed when the puzzle is reproduced: after

> 1 f6! Qb3 2 f7! Qd1+ 3 Kh6! Qf3 4 Kg7 Qg4+ 5 Kh7 Qf5(h5)+

> (or 5 Kh6 Qf5, or 5 Kf6 Qh4+ etc.) 6 Kg7 Qg5+ 7 Kh7 Qf6 8 Kg8 Qg6+

> 9 Kf8 (avoiding the usual 9 Kh8?? Q:f7 because of the unwelcome 10 Nc2)

> 9...Ka4 10 Ke7 etc. Black can choose to finish with (48 Kg8 Qg6+ 49 Kf8)

> Ke5 50 Ke7 Qd7+ 51 Ke8 Ke6! and then the only move to complete the

> 50-count is 52 Nc2!, ironically the same suicidal play that might have

> undone White 43 moves earlier.




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