Illegal Position Contest!

#5769
Black has promoted 4 dark square bishops and 2 queens. Black must have captured 3 white pawns to get past them to promote 6 pawns. The last move must have been ...Bxf6+. Thus 3 + 1 = 4 white men must be captured. White has 13 men and thus only 3 can be captured.

ok

The 6 black promotions do not require 3 white pawn captures. The two captured black rooks can already promote 2 blacks, by moving the capturing white pawns out of the way.

A white pawn that captures a black rook to let a black pawn promote on a dark square ends up on a file where it will also promote on a dark square, along with another white pawn already on that file. After it happens a second time, White has four pawns that will promote on dark squares. White's one remaining capture isn't enough to let White to promote to the needed two extra light-squared bishops.

It has little to do with the pawn already on that file, as that pawn is still opposed by another black pawn.

Since that pawn is opposed by a black pawn, it follows that the black pawn is opposed by that pawn. So after the black rooks are captured, there are still six black pawns opposed by white pawns on the same files. Black needs a capture for the final check. The two remaining captures by Black and one remaining capture by White aren't sufficient to let five of the six opposed black pawns get through, so Black cannot promote seven pawns and the position is illegal.

Is this an illegal position?

opps this

Wow, the White pawn promotes to a bishop by moving from g2 to g1!

This is an illegal position.
It happens many times in real games.
Two bishops in the same color squares.
Considering pawns was not promoted

I think this is possible lets analyse.

White always begin playing

1. White move a knight.
2. Black move pawn to the position shown in the picture.
3. White move the knight back to the original position.

#5779
This is illegal: a white pawn cannot go back from g2 to g1 and promote to a bishop.

5781
This is legal: a pawn can promote to a second dark square bishop.

5782
With white to move: 1 Nf3 d6 2 Ng1 d5

2 captured white pawns and 1 captured black pawn are enough to let 5 black pawns and 4 white pawns promote.

You are right. I noticei it,  but I was already in the bed.
I corrected my post.
It happens because many times people put the bishop in a different color than its original, due of an error.

Thanks for your reply!

 

#5786
Illegal indeed. Last move f4 gxf4++ e.p. would be possible, but then Kg3 was in check from Bb8.
Discovered checks ...Kc7-c6+ or ...Kd6-c6 are impossible as then the black king would be in double check from either b6 and Na8 or Bb4 and Rd3 respectively.

Kd6xc6+ seems possible to capture a pawn that itself took en-passant.

Except that it would leave Bb8 impossibly trapped by its own pawns.

Not if at least four black pawns have to promote on dark squares and all four white pawns have to reach files where they can promote on light squares.