Illegal Position Contest!

Also note the rook can capture something on c1, from the first tank. Black king c4, white captures on d3 with with c pawn check, and the king goes to b3 from there.

Also

I'm sure my 45-move proof game for this legal position can be shortened.

At this point people are spamming in positions like this

and hoping that we won't see the illegal-ity but it's (I guess) not what this thread was designed for. If you actually want to post something obviously illegal I suggest try making a new forum dedicated to something like that (I actually barely put in effort for most of my submissions so yes, this also applies to me. I literally threw in just like, 5 pieces and used 1 minute). (Yes you can upvote or downvote or reply or whatever or call it yap etc) but throwing in zero effort absolutely ruins the purpose of this forum.

I wonder if this position was also intended as an example of spamming with an obviously illegal position. (It might take as long as 10 seconds to notice that White has no promoted pieces and the white bishop has illegally moved from f1 to d1.)

But his heart's in the right place.

I believe you're right. He could remove the h2 pawn and post the resulting legal position in the Shortest Proof Game thread. There, the task is to reach the position in the fewest moves.

There is one?

Could the missing h2 pawn have captured black pieces and promoted to a bishop on a light square to then slide into d1?

If the position without the h2 pawn shows up in the Shortest Proof Game thread, someone there will shorten my 37-move first try. (Forums > Fun With Chess > Shortest-Proof-Game Challenge)

Here is my try at an illegality proof for this position.

There are no promoted pieces on the board, and the final move is O-O by White. Black's only capture is Pa6xBb5, and White has to cross-capture Pb2xQc3 and Pc2xBb3, to let the a1 rook come out. The h8 rook can't leave the 8th rank via the a-file, since the c8 bishop can't move until Black plays Pb7-b6, and by then there will be a white bishop at a7. So Black has to play Pf7-f5 and Pg7-g6 to get the h8 rook out. One black rook has to reach h6 before there is a white pawn at h5, and the other has to reach h3 before the black knight gets to h4. But then the knight can only get to h4 from f3 or g2, checking White on the way and preventing the final castling.

The game below is a failed attempt. Every piece is in the right place, and White is ready to castle, but castling is illegal because the king has already moved.

Nicely done! There is one tiny nitpick (black’s h8 rook may have arrived at h3 before g2-g3 was played, but then a6xBb5 hasn’t been played yet so black’s other rook couldn’t have moved over to h6) but apart from that all the details are there.

Should I do it?