THE CHAIN OF PROOF IS BROKEN
Suppose a position has a unique proof game for a given
number of moves. Does it follow that the prior position also supports a
unique proof game? The surprising answer is no, and
here are some examples to prove it.
{A}
A.G.Buchanan
Original 

{B} Thierry le Gleuher
Hon. Mention, Messigny 98
M6 Phénix 66, September
98 

{C}
A.G.Buchanan
3943 Phénix 106, April 2002 





(15+16) a) PG in 5.0.
b) Is the position before Black's last move a correct PG in
4.5? 

(16+15) a) PG in 4.5.
b) Is the position before White's last move a correct PG in
4.0? 

(15+13) a) PG in 6.0
moves. b) Is the position before Black's last move a
correct PG in 5.5 moves? 
OK, so you can see that it's just a trick involving
castling or en passant. Michel Caillaud's example shows how the trick
can be harnessed to ensure the integrity of a deep position.
My ambitions are more humble. In {E},
{F} & {G}, I am
looking for quick e.p. positions where there is no check in the final
position. {H} is I think the shortest PG of this type involving castling. Compare this with Thierry's {B} which is the
shortest PG
involving e.p.
{D} Michel Caillaud
Probleemblad, 1998 

{E}
A.G.Buchanan
3944 Phénix 106, April 2002 

{F}
A.G.Buchanan
Original 





(13+12) a) PG in 22.5.
b) Is the position before White's last move a correct PG in
22.0? 

(15+15) a) PG in 6.0
moves b) Is the position 2 moves ago a correct PG in 5.0
moves? 

(13+16) a) PG in 5.5.
b) Is the position 2 moves ago a correct PG in 4.5? 
{G} Thierry le Gleuher
version A.G.Buchanan
Original 

{H}
A.G.Buchanan
4304 Phénix 120, August 2003 







(15+15) a) PG in 5.0 moves b)
Is the position 2 moves ago a correct PG in 4.0? 

(15+14) PG in 5.0. Is the position before
Black's last move: a correct PG in 4.5? 


Solutions
Back to home
page
