Legal position?

Black

White

Originally posted by heinzkat
Black
[fen]8/8/3KPk2/8/8/8/8/B7[/fen]
White

Nope, not legal. [I suspect the diagram did not come out as intended.]

Originally posted by SwissGambit
Nope.

SOLV'D (SwissGambit)

Pointe of the PM by Jirakon
Nope, not legal.

SOLV'D (Jirakon). The answer is very complicated, as you can see...

Originally posted by SwissGambit
Nope, not legal. [I suspect the diagram did not come out as intended.]

The board is upside down and white has just promoted a pawn to a bishop. ... else its illegal.

Originally posted by wolfgang59
illegal.

SOLV'D (wolfgang59)

Sorry I should have PMed you but didnt think I was right.
(I NEVER SOLVE CHESS PROBLEMS!) LOL

b) wK->d7. Why is this position not illegal anymore?

Originally posted by heinzkat
b) wK->d7. Why is this position not illegal anymore?

I can't see a reason... maybe I'm just not good at this. Did you mean wKd5?

Originally posted by heinzkat
b) wK->d7. Why is this position not illegal anymore?

e. p.

Originally posted by David113
e. p.

Good one! Didn't consider that.

Originally posted by David113
e. p.

Then why was e.p. not possible in the 'a)' part of the problem?

Originally posted by heinzkat
Then why was e.p. not possible in the 'a)' part of the problem?

bPe7 would put wKd6 in check (i.e. both kings would be in check simultaneously, bK from wBa1).

Originally posted by curseknight
bPe7 would put wKd6 in check.

Yes... therefore the previous moves cannot have been d4-d5+, e7-e5, d5xe6 e.p.+, since White cannot have played d4-d5 while his own King was in check. Therefore, the first position is illegal.

With the wK->d7 the previous moves can/must have been (in order to reach the position) d4-d5+, e7-e5. d4xe6 e.p.+.

I welcome better thought out explanations.

(on a sidenote, 'can have been', is there a better construction to say this?)

Originally posted by heinzkat
Yes... therefore the previous moves cannot have been d4-d5+, e7-e5, d5xe6 e.p.+, since White cannot have played d4-d5 while his own King was in check. Therefore, the first position is illegal.

With the wK->d7 the previous moves can/must have been (in order to reach the position) d4-d5+, e7-e5. d4xe6 e.p.+.

I welcome better thought out explanations.

(on a sidenote, 'can have been', is there a better construction to say this?)

"were possibly" might be useful there. Good problem, at first I could not see how en passant was possible, forgetting the pawn check.