Illegal Position Contest!

ok

Emmm how exactly did the pawn get to a7 

Probably not this obvious but this is from my first glance

In case any question should arise about copyright, I will post the source of that position.

Hans Gruber
939 Augsburger Allgemeine 02/04/1977

In theory that should be done anytime you post a problem composed by someone else, but that seems to rarely happen here. I used to do that regularly, and will try to start doing it again.

uhh it marched up there with blacks a pawn taking twice.

so white has 13 pieces. then takes on f2 so white has 14 pieces. and  #4627s logic so 15 pieces.

nothing wrong with white.

After the black e-pawn captures the white f-pawn, the white e-pawn can promote to a bishop, for example, which can be captured by the black a-pawn on b5, allowing the white a-pawn to reach a7 without making any captures.

white to move

This is an illegal position.

Can anyone tell why?

(Black to move.)

Hint: Look at the position of the pieces worth more than 1 point. The pawns are fine.

A little too easy. Black has eight pawns and thus no promoted pieces, so the c8 bishop could never get out but jumped to f5. That's only legal if your opponent is looking the other way when you move the bishop.

White can capture once.

Black can capture four times.

Doubled Pawns on the f-file: 1/4

White's a-Pawn is ahead of Black's: 2/1 or 3/4, so we go with 3/4

White's g-Pawn is ahead of Black's: 1/1 or 5/4, so we go with 1/1

White's original g-Pawn is missing and didn't promote: 4/4

Black's only missing man is the c-Pawn. Promotion would've required a capture (5/4) and promotion would be mandatory to allow for White's h-Pawn to capture to the g-file.

The position is illegal because there were too many captures used to reach it.

That is a valid explanation. Here's another way to look at it.

White is missing four pawns and Black has four captures, so every capture by Black must be of either a white pawn or a promoted white pawn or a white piece replaced by a promoted white pawn. How close can we get to making that happen? The black c-pawn can capture the white d-pawn. The black e-pawn can capture the white f-pawn. The black a-pawn can capture the promoted white e-pawn. The white h-pawn can capture a promoted black d-pawn. That leaves Black needing a final pawn capture, and White with a pawn needing to be captured, so the piece count is proper. But the black pawn is on the b-file, and the white pawn is on the g-file.

The position is illegal because there is no way to make the required final pawn capture.

Now that the illegality is settled, is anyone going to try to solve the position as a White to play and mate in 2 problem (without using the analysis board)? That should appeal to the lurkers who aren't into illegal positions and proof games.

Here's another one. (Really I'm not going to make them hard, if you want me to, feel free to say so.)

Make them hard.

I vote for hard.

is this legal?

No.

.

That one's harder, but I think it's illegal because both sides should have a king. (Also according to art.1.1 there should be a board.)

White's d-Pawn captured the wrong way.