Underpromotion Puzzle

Lol nice...

The second-to-last move is unfortunately flawed.

Also, I believe this is a variation on another puzzle I have seen with a very similar solution.

Ha! Ha! It's a funny puzzle! All the move are forced in fact. It's like a mechanical machine!

Just for fun, I entered that in Chessmaster 9000 and see if it can solve it and yes, it solved it. I was curious to see if their algorithm would promote as knight since it was what is required to avoid a stalemate.

Thanks for sharing!

 The 12th move is a8=B, not a8=Q. And I did use ideas from a book I read 2 years ago.

cool, but how did the bishop end up on e1?????????

You believe correctly.

D.H. Hersom, The Fairy Chess Review, 1936

The diagram is flawed. The bishop on e1 is illegal!

true

there is no way for that bishop to get there with pawns taking up the only 2 ways it can get there