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MatPlus.Net Forum Misc An interesting retraction problem
 
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(1) Posted by Bob Baker [Sunday, Aug 18, 2019 23:07]

An interesting retraction problem


Here is a problem I found interesting. It was composed and posted yesterday by 'Arisktotle' in one of the chess.com forums.

Find a legal sequence of moves leading to the position below such that the player who made the last move can retract it and replace it with a winning move.


(= 4+2 )

 
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(2) Posted by Rewan Demontay (Real Name: James Malcom) [Monday, Aug 19, 2019 05:19]; edited by Rewan Demontay (Real Name: James Malcom) [19-08-19]

It's not the fastest possibile PG by far, but it's still something-

1. g4 f5 2. gxf5 e5 3. d4 exd4 4. Qxd4 Bc5 5. Qxc5 Nf6 6. Qxa7 O-O 7. Qxa8 h6 8. Bxh6 Nh7 9. Qxb7 Rf6 10. Qxb8 Rg6 11. fxg6 Qg5 12. Qxc7 Qxh6 13. Qxd7 Qh4 14. Kd2 Qxf2 15. Kd3 Qxg1 16. Ke4 Qxh1+ 17. Ke5 Qg2 18. Ke6 Qxe2+ 19. Kd6 Qxc2 20. Ke7 Qxb1 21. Ke8 Qxa2 22. Qxc8 Qxa1 23. Bc4+ Kh8 24. Bg8 Qxb2 25. Qf5 Qf6 26. Qxf6 Nxf6+ 27. Kf8 Nh7+ 28. Bxh7 1/2-1/2

The retraction move is easy: gxh7 instead of Bxh7.


I have interacted with Arisktotle myself on the chess.com fourms before. They are a prominent problemist over there.
 
 
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(3) Posted by Siegfried Hornecker [Monday, Aug 19, 2019 05:49]

Sadly I can't find it in the forum, as I am really curious as to what the solution is. I tried everything, I think, and nothing works. Of course Rowan's idea still is a draw, as the only way to get Ph2 to the g-file is per stalemate.
 
   
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(4) Posted by Geir Sune Tallaksen Østmoe [Monday, Aug 19, 2019 10:00]

Retract Ph5xPg6 and play 1.Bg8. Then Black has one pawn too many to get stalemated after 1...gxh5 2.h4 or 1...g5.

Pf5xPg6 does not work, I think, as after 1.Bg8 gxf5 White does not manage to stalemate Black while blocking the f-pawn.
 
   
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(5) Posted by Bob Baker [Monday, Aug 19, 2019 11:25]

Geir has found the solution. When I posted my reply on chess.com, I gave the clearly legal position below with the moves 1. Bh7 Rg6 2. Nxg6+ fxg6 and noted that instead of hxg6, White has a mate in 14 starting with Bg8. Arisktotle commented that, as a composer, he prefers the mate-in-5 variation after ...Pgxh5 since it forces the unique winning move h4! And it's true, once White finds the first move, it's Black's only chance to give White a unique winning move that's not obvious.

Geir is correct that with the h5 pawn on f5, the result is a draw. Siegfried is correct that Rewan has reached the final position, but has given a retraction that produces a drawn position. As I imagine Siegfried did, I failed with every possible king capture and bishop capture before hitting on the correct pawn capture for White's last move.


(= 5+4 )

 
   
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(6) Posted by Guus Rol [Saturday, Nov 28, 2020 17:01]

Thank you for posting that. I forgot all about that problem and now take vitamins to recover my memory. One day I will remember!
 
   
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(7) Posted by Andrew Buchanan [Saturday, Nov 28, 2020 18:25]

Amiright that White has 3 winning retractions: Ph5xPg6, Pg5-g6 & Bg8xPh7, but only the first is derived from a legal position?
 
   
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(8) Posted by Guus Rol [Saturday, Nov 28, 2020 19:32]

That looks about correct. I'm somewhat serious about my memory though it is returning now that I am tackling the position again. SF confirms what you suggest and its analysis appears correct.

I am somewhat sad about posts disappearing mysteriously from chess.com (haven't searched for this one) as it destroys compositions I can't even recall having made anymore. Not all my stuff is in my own topics, I often place them as comments in different threads. By the way, I started to occasionally scan the last months and add the best content into a document. Most not retro though.
 
   
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(9) Posted by Andrew Buchanan [Sunday, Nov 29, 2020 04:46]

Hi Guus,
In chess.com in a browser on my PC, I discovered yesterday that for message chats, I can get the older messages to appear by dragging the slider on the right to the top, and then repeatedly dragging it down and up. It's quite time-consuming, but with this undocumented feature I can go all the way back to the beginning of our conversation.
 
   
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(10) Posted by Guus Rol [Sunday, Nov 29, 2020 09:43]

Thx! I'll check that! Btw, most of my lost material is (was) in the forums. I commonly communicate in the public places; private exchanges are for special purposes and persons :-)
 
 
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MatPlus.Net Forum Misc An interesting retraction problem