Shortest-proof-game challenge

This brilliant composition by André Hazebrouck won 1st Prize in Schachmaty w SSSR 1978. It's mate in 1, but to determine whether it's Nc8# or Nxb2# we need to determine who's to move. Would love to see a shortest proof game.

A wonderful retro worthy of its 1st place. As for the SPG, it is in 57 moves: 37 moves to get to the "critical" position, then 20 more to get the final pieces in place.

From the illegal position thread. I have an 88-move proof game, but this time I'll leave it for you guys to shorten.

Thanks! That does indeed look minimal, since every move Black made was necessary, modulo some equal length alternatives, like g7-Bh6-Be3-g5 instead of g5-Bg7-Bd4-Be3. Did you create this SGP or was it known before?

I created this SPG, although I had to peek at the solution for the retro for the final moves. Didn't realise black's hxg capture could happen in front of the white g-pawn, but oh well

After figuring out the final moves of the position, all that was required to do was reach the critical position as quickly as possible. Some experimentation leads to the fact that black is slower than white, so we just have to optimise black whereas white has free moves available. The other thing is capturing Bc1: a black knight could capture it then move to d3 (for e2xd3) for only 2 extra moves, and capturing it with 1 or 0 additional moves is impossible.

If you like proof games, you might enjoy this new blog of mine: ‘Rematch’ and a retro chess problem that baffled Kasparov. As the title suggests, it's a difficult problem...

Hey everyone! I’m a total beginner at chess and looking for someone to play with. I’d love to get better and learn some strategies along the way. Anyone up for a game?

Lol why not

I can bairly play myself so should be a decent match

The closest I got is 6 moves.

Close but no cigar!