Illegal Position Contest!

White's light square bishop could not have possibly gotten out, since the e and g pawns haven't moved. Also, there aren't enough of black's pieces gone for the b or a pawns to have promoted to a bishop on the kingside, since it couldn't have gotten out on the queenside and all kingside pawns are still there. 

How many captures would the white c-pawn need to promote, and how many were available?

3 were available, 4 were needed; the f and g pawns could have been captured, and the kings rook. Even though the black light square bishop was missing, it couldn't have been captured by the pawn since the black b and d pawns are still unmoved. 

That's what you needed to complete your proof of illegality. Here is a another way to say it.

White's f1 bishop was captured at home, so the bishop at c2 must be a promoted piece. Black has 12 men on the board, so White has made four captures. One of them was of the bishop at c8, which was captured at home, leaving three captures for  the white c-pawn, allowing it to reach the f-file, where it can only promote to the wrong color bishop, making the position illegal.

I had expected December_TwentyNine or DefenderPug2 to weigh in on this one.

No. It's not illegal to be checkmated.

If you would still like to do something with this position, prove it would be legal if the c5 pawn were removed. ("Prove legal" means construct a proof game.)

Are you referring to the position with the c5 pawn removed? It's a legal position, and I'm suggesting you could contribute by showing us a proof game.

lol i cant believe this forum was created in 2016-

Chess has a bunch of subjects that were introduced a long time ago, and some of them still haven't been "solved."

yea ikr but im surprised this forum is still active lol

It's probably good for you to be surprised occasionally. You should take a look at the thread  Forums > Fun With Chess > Shortest-proof-game challenge. It was started in 2011. There are a couple of recent positions there for which no one has yet posted the first proof game. You could be the one.

That's definitely a better way to say it

How are you coming with your proof game showing that the position at #5962 is legal if the pawn at c5 is removed?

I don't believe it's incredibly difficult. I'll give you the choice of working on it some more or asking to see my proof game.

Here's the position without the c5 pawn. As you said, a white knight has to capture the c8 bishop. But now White still has four captures left to get the white c-pawn to a file where it can promote to a light square bishop. That includes capturing the black a-pawn, which doesn't have to still be a pawn when it gets captured.

nf3 e6 ng1 e5

I think it's fine. A 51.5 move game is not bad for a first try. The proof game I made for it is 33.5 moves and is probably not the shortest, but any legal game works to confirm the position is legal.

If you've decided you like working on proof games, you should check out Forums > Fun With Chess > Shortest-proof-game challenge

#6000

lol i saw and noticed it was at 5999