(Retro) Chess Detective 2: The Two Roads


This is a stunning but simple proof game by American composer Mark Kirtley (published in "The Problemist Supplement" in 2012). There are exactly *two* different ways to reach the final position after White's 8th move. Can you find both? Mark is a specialist in this demanding kind of composition.




Nice - one with castling and one without!


Method 1

1.b4 a5 2. Bb2 a4 3. Bxg7 Nf6 4. Bxf8 Kxf8 5. Nc3 Kg7 6. Nxa4 Rf8 7. c3 Kg8 8. Qb3


Method 2

1. b3 a6 2. Bb2 a5 3. Bxg7 Bxg7 4. b4 Bc3

5. Nxc3 a4 6. Nxa4 Nf6 7. c3 0-0 8. Qb3


At least I found one of the two methodes I shall post it I hope the second I find later.




And the second I find too!



Hurray well done! Can you figure out why each solution has 8. Qb3 at the end, even though it happens to be the same move in both solutions?


Thanks it came suddenly to me in the morning the other I found quickly after it.

Na I found out quickly that Qb3 must be made in one move from d1 otherwise it would took to long.

For example something like Qb1 x b2 and then Qb3 took to long.

So Qd1-b3 could only follow direct after c3. That means that the Nc3xa4 manouvre must be played before this otherwise the field c3 was allready occupied by the pawn.

First I found out that after 1.b4 a5 and take on g7 and take back on g7 to sac on c3 did not worked out because I had not enough moves with the pawns. And so I came on 1.b3! to and 1...a6 to do that.

Later I found out that 1.b4 still worked but than after If black did not take back on g7 and white take on f8 next move and black will not castle he will be able to get the same position.






The reason for 8.Qb3 is because without it, one of the two solutions has a shorter version in 6.5 moves. This would mean the problem has to be specified to be *exactly* 7.0 moves, which is generally regarded as a defect.