# An original retro problem #11

• #1

Legal or illegal? what do you think?

• #2

I think it has to be illegal.

• #3

Well, you have to provide analyse with your answer, Timothy. Why do you think this is illegal? - and, "because it looks like it" is not good enough

• #4

I think blacks last move must have been king from c7 to c6, as that's the only way the bishop could have gotten him in check, it would have to be discovered. I say... legal? edit: wait! c7 is check! So the queen must have snuck in there before... impossible. Illegal?

• #5

Ah, yes. The black king must have moved from c7, but he would be in check from the queen on a5.

Is there anyway around it?

• #6

I don't see how the queen could have snuck in thereto check the king, it would have been blocked off by white pawns... And white has all his pawns, so no tricksy promotions have occured... Am I right?

• #7

You are observant, but it might be possible!

Maybe, a discovered check...

• #8
shoopi wrote:

Well, you have to provide analyse with your answer, Timothy. Why do you think this is illegal? - and, "because it looks like it" is not good enough

Haha! Ok - I quite possibly am missing something, but - the check! It cannot be a promoted DSB because all (black and white) pawns are present. For it to be legal, it would have to be discovered. Furthermore, the only piece capable of discovering the check is the black king. I don't see how that is possible, so I think the position is illegal.

• #9

Oh and also coordinates are given so nothing tricky there.

• #10

Legal.

• #11

I saw one possibility, white are up and black are down. So the black bishop in b8 is in reality on g2. I tried: -1 g3xf4, Kf2-f3+. It could be the solution but... there's a problem, (a big one!) black have 15 pieces on the board, only the light square bishop is missing, so it's not the bishop that white pawn captured on f4 (dark square). So the last move can't be g3xf4. I don't see anything else so I think the position in illegal.

• #12
BigDoggProblem wrote:

Legal.

Brilliant! You must be right. I got it wrong again, shucks.

• #13

Timothy_P wrote:

BigDoggProblem wrote:

Legal.

Brilliant! You must be right. I got it wrong again, shucks.

I agree

• #14

I notice that it has to be a rook there, clever.

• #15

Yes that is the correct final sequence. The position is legal, good job again.

• #16
The knight can get to h1 before g2-g3. Here is a (rather inefficient) complete move order.
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