So you like retros

  
Problem

So you like retros?


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Lionel Vidal    (2007-02-11 19:54:36)
So you like retros?

At first, I did not dare to post retros problems...
You did find the last retros posted here difficult? Really? you must be kidding :-)
Now *this* one you may find challenging :-)
It is from J. Haas (1973) and the very nice question is: remove a man (other than a king) to make the position illegal!
(only one solution, and yes, there are 3 black rooks in the diagram :-))
ChessPosition (see diagram)
8
7
6
5
4
3
2
1
a b c d e f g h




James Klemm    (2007-02-12 07:29:27)
it looks like

the pawn in front of the white kingbecause it would be check and no possible move could cause that check


Lionel Vidal    (2007-02-12 08:58:32)
A starting point...

The first question should be: is the position as it stands legal? Or in other words, how to reach that position through legal play?
oh, and sorry if I was not clear enough, I meant to remove a piece! (a pawn is too easy :-))


Lionel Vidal    (2007-02-12 11:20:57)
White missing pieces

Let's look at the missing white men. The only missing black pawn is the h-pawn, that has promoted to produce the third black rook.
It could not have promoted at g1 (because the rook would have been trapped). Therefore it must have made captures on the g-file, the f-file and at e1.
Another pawn capture took place at b6 or b5 and the WRh1 was taken at g1 or h1.
This is all for the 5 missing white men!
Next step is: have you an idea to disentangle the top left corner?


Lionel Vidal    (2007-02-14 21:53:43)
You cannot retract a4-a5!

Here is a second hint: white cannot retract a4-a5.
Do you see why? At some time in the past, we had WBc1, WPb2 and BRe1. The black N went to a1, white played b3 to free the bishop, but if the a-pawn were on a4, the BRe1 could never have escaped!
Hence a4-a5 occured long ago to free the promoted black rook...
Now, try to prove that no retractions are possible from Pa5,Pb5,Qa6 and Rb6 (count the white captures!)...