Black and White

Kicked myself for giving up but I never really tried to do one of these before.

Very nice book for introduction to the retrograde field! And if I remember well, one of the best selling chess books ever. There is a follow-up book as well, something like "... arabian (k)nights". I had both, but they seem to have magically disappeared.

I suppose you do know the solution to the diagram now?

Here is an even more mysterious diagram which I discovered myself but I likely was not first. Don't think to long about it. It's not a joke but it may need an explanation. The question is "who is on move?".

I'd prefer not to provoke discussion about move phases this time, so let's phrase the answer as: white just captured on b6 (Arisktotle's diagram). And you do need DR.

@Remellion: Yes, more accurate would have been to ask for who moved last, but I didn't think the OP would notice the difference. Had I known you were to land here ...

KxNa8

Yes op did not know the difference but now with Remillions post  White just captured b6,Who is on move implies (in my opinion)blacks move b8.  I find these just foreign to my thinking process but getting interesting because of that.

@ ytzd Yes that is it (just in case you weren't 100% sure)

@sameez1: There is a relatively new rule in chess (nineteennineties, I'll look it up later) that says that a chess game ends at the very momment that the only possible result is a draw. The position is then considered "dead". For instance, the diagram itself is dead and play stops here.

But something interesting has been going on earlier. When assuming that black moved last, then you can see that, whatever that move was, draw was already inevitable. Which means the game already ended at that point and could not progress to the diagram. Conclusion: white played the last move. Was the position dead before white's last move? No, not necessarily, since he might have played something like KxRb6. Only after capturing the rook, the game was dead (diagram).

Since white played last, black is to move in the diagram, but of course he will never move because the game is dead.

Remember, this can also happen to you in a game. A dead position is drawn even when your time expires. I am not sure chess.com knows about this, though!

@Ariskotle : the first one that came up with this idea is Andrew Buchanan, more than 12 years ago. He put the king on c6 instead of b6 and asked : who played the last move ?
It's possible to use this idea to create more complicated stuff. Here is a study I just composed.

White to play and win.
First task is to prove the last move was g7-g5 and not g6-g5 and second task is of course to solve the study.

If I recall correctly, I found the "two bare kings" about 15 years ago but I won't fight with anyone about it. I know Andrew well, he practically owns DR! And indeed, the king is better on c6 than on b6.

That's a scary study! Makes you check every pawn ending you ever produced or saw and test it for DR. So easy to overlook! By the way - as I proudly tell everybody - one of my prize winning SPGs is really cooked by DR. But judges are not so wise on the subject, especially when intertwined with interpretations of retro-conventions.

Your study is also quite an intricate pawn ending. Without access to a 7-piece tablebase I actually had to solve it! First, counterintuitive e.p. capture (hxg6) followed by another counterintuitive king move (Kh3). After black forces white to play g4, his king runaround proves one move too long; the wK arrives at c6 and wins. Lots of content!

Wow, a SPG cooked by DR, that must be interesting. Every possible last move including yours lead to stalemate ?
But actually it's not cooked by DR because according to the rule of composition, DR is considered fairy chess. I personnaly found it rather stupid because it's just following the FIDE rules, but many problems especially studies would have to be ended before stalemate, which would be a shame.

Is that so? Only for the retro type? Recent change? Do you have a link?

In my problem, the last move would inevitably lead to a repetition draw. Not an issue in FIDE chess where draws must be claimed, but with the convention on "automatic draws" it turns into an inevitability and is therefore susceptible to DR. Unless DR does not apply, of course!

Actually I was mistaken : "

Article 17A – Dead Position Rule

Unless expressly stipulated, the rule of dead position does not apply to the solution of chess compositions except for retro-problems.'
http://www.wfcc.ch/1999-2012/codex/
So your SPG is cooked by DR only because it's a retro-problem...

The board is seen from black's perspective (coordinates are not listed but assumed).  The position can be arrived at like this:

The other position can be arrived at like this:

Post 3 could have arrived from any piece on a8.  For example, play could continue with 1...Qa8 2. Qxa8 Kxa8.  Ignoring the immediate stalemate, white would have the move.  However, white may have played 1. Nb6+ Qxb6 2. Kxb6 and this time, ignoring the immediate stalemate, black would have the move.

I will reread the rules/conventions. Article 17 used to be different. But anyway, if I were to claim this SPG is not a retro-problem, then the automatic repetition rule would not apply which I need for an unambiguous fulfllment of the stipulation. In all cases, I'm a dead! That is, once the interaction between rules and conventions is properly understood.

@JonWB81 very clever but does blacks perspective follow the conventions the other posters are speaking of.I don't know but it would seem that with the precise proof being most important that the perspective would always be with white unless specified. 

post #1: The standard assumption for diagrams is that white pawns go upward and black pawns go downward - unless specified differently. And there is a legal explanation for the diagram from that perspective. Keep looking!

post #3 and post #11: The other two diagrams are related to a FIDE rule you don't know about regarding "dead positions". Please first read the rules on this before you try solving them. Link: http://www.janko.at/Retros/Glossary/FideLaws2004.htm article 5.2.b. Remember that these rules also apply to positions before the diagram!

JoachimJo: That's a nice retro study. There are very few of those, let alone one using DR. I hope you're OK if I put it in PDB.

Arisktotle: wow I didn't know you independently came up with the dead position idea which the 1997 rules first permitted. You never mentioned that before: such modesty. A French guy called FPC also stumbled across the concept in Jun 2001, but had been pipped at the post by Andrew, who first ran into the possibility in Los Angeles in Sep 2000. The Codex since 2015 states that by default it only applies to retro problems, so it's a lot less controversial.