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Jesper Norgaard
11-10-2009, 05:47 PM
It's a blitz game. Black to move and checkmate in 2 moves. Can you find the solution?

2KP4/8/1k6/3p4/8/8/8/q7 b - - 0 1

Desmond
13-10-2009, 10:56 AM
I guess it depends on your reading of the promotion laws. If White does not promote before pressing the clock then people here have argued Black may place his own piece on the board. In that case we can mate in 1 with ...d8=R and Qf6.

Or if Black cannot promote White's piece and White cannot on his next turn either, the 1...Qg7 2.Kb8 Qb7# appears trivial.

Jesper Norgaard
14-10-2009, 09:27 AM
Or if Black cannot promote White's piece and White cannot on his next turn either, the 1...Qg7 2.Kb8 Qb7# appears trivial.
This is in fact the only solution. Appears trivial I admit - I guess I am not much of a composer. However some consideration goes to the (lack of) piece switch in the promotion. If it is a game and not a study, there will be an arbiter. I am assuming White actually pressed the clock although I didn't say, to actually make it blacks turn. Of course just after releasing the last piece it would technically be blacks turn, although since the promotion is "not finished" technically he would not have the move. That would happen only when white releases a *new* piece on d8.

In a normal or rapid game, no matter what solution we suggest, it would be naught because white could always claim that his d7-d8=P was an uncompleted or illegal move and the arbiter would allow the position to be established back to the promotion (so white could correct it). Not so in blitz. Whether the last move was the illegal d7-d8=P or it came before it, with 1...Qg7 black makes the move d7-d8=P legal and thus white can't claim that the promotion must be changed/completed.

The other point of this problem is that white is worse off with the pawn on d8 than without it. If there was no pawn on d8 then black would not have mate in 2, but only mate in 3 in a number of ways. Thus white can't move the pawn, but can't take it either, for instance Kxd8 is illegal. Also the pawn has a third (perhaps hidden) effect, 1...Qa7?? is stalemate! But Qa7 as an idea is of course weak, even after the illegal 2.Kxd8 it would still only be mate in 3.

I am sure a real problem composer would not be impressed, but it shows I have a knack for the consequences of those strange laws of FIDE. Once a check from 3 opponent pieces was not a check according to the old FIDE laws, so a composition could be made where one side deliberately provoked more checks on his king and therefore was not in check anymore.

If you expected a weird solution like this one:

White: Ke5,Bf6,Rg7
Black: Kh8

White to checkmate in move!

... then I am afraid I disappointed here.


I guess it depends on your reading of the promotion laws. If White does not promote before pressing the clock then people here have argued Black may place his own piece on the board. In that case we can mate in 1 with ...d8=R and Qf6. A nice attempt, but nowhere does it say in the FIDE laws that the opponent can choose promotion piece if the player himself does not, so I will have to overrule that. Although I would also add that it would be mate in 1, not in 2, but some would say "all the better!".

Jesper Norgaard
14-10-2009, 10:24 AM
I guess one last point is that the pawn on d8 is still "alive" so that it is not a solution to play 1...Qa4 Kb8 2.Qe8# since the pawn on d8 is still protecting the king.

Desmond
15-10-2009, 10:18 AM
This is in fact the only solution. Appears trivial I admit - I guess I am not much of a composer. Sorry, no offence intended. What I meant was that it looked too easy so I thought I was probably wrong but I thought I'd say it anyway. :)

Jesper Norgaard
15-10-2009, 11:21 PM
Sorry, no offence intended. What I meant was that it looked too easy so I thought I was probably wrong but I thought I'd say it anyway. :)
No offense taken, Boris. I would probably have called it trivial in my solution, but you got it first. Still not trivial enough to make the computers find the solution for you (they won't accept the pawn on d8!). Since FIDE rules allow blitz games with a host of strange and illegal situations, but they are still valid games, then I think in fact it is the software that is wrong(!). The software should perhaps warn you but accept these unusual games. The exception would be promoting to an ashtray - I can forgive the software for not allowing that :doh: