Most Difficult Mate in 1 ?

I saw this problem in a Jennifer Shadade lecture (around 31:40).

White to play and mate in 1 (White started at the bottom of the board as usual.)

E3 to A3 for the first

Qd8 and Qb7 are both mate

Qd8 kxc6

Qb7 isn't the hardest mate ever...

1.Qb7 is not correct.

I disagree.

It is because the black pawn can't take.

All hail the chess.com PGN viewer.

Checkmating the King has nothing to do with chess at all? Nice.

You typed in the move. I simply copied the FEN and made a move. Big difference.

I really messed up there - d8=R# is not legal, the P is pinned.

What I meant is - why the hell has each side promoted 2 extra bishops instead of queens? Mate would have happened ages ago if this hadn´t been the case. That´s what I meant with "nothing to do with chess".

I could easily have done the same in WinBoard, which allows me to turn off legality checking. But that's not the point. The point is that 1.Qb7 is not legal.

You must have changed how the queen moves then.

Mate in 1´s all very well, but I prefer this sort of problem: what´s the shortest route to mate here?

White to move:

I see nothing wrong with dxc8Q(R)#

The bishop can interpose, delaying the checkmate.

The position isn't legal, is it?

Black has made 3 pawn captures, and White is missing two pawns and a light-squared bishop.

White has made at least 2 pawn captures, and Black is missing a light-squared bishop, rook and knight.

Now how did the black pawn end up on f2? It must have come via h4 and g3 (we don't have enough captures available for anything more exotic).

So it must have captured two pieces on black squares, which means that:

(1) White must have promoted both his a and b pawns. (This also means that White has actually played 3 pawn captures.)

(2) White's white-squared bishop must have been captured on a6.

How did the bishop get to a6? White must have played g3 to release the bishop, then later played g4 and (after the Black pawn has reached f2) hxg3.

So what was Black's last move? It can't be a capture or a pawn move, because we've accounted for those already.

Qc8d7 doesn't work because there's no previous move for White (how did he give the rook check?).

Similarly Kc8c7 doesn''t work because White can't give the queen check on a8 without a capture-and-promotion, and we've already accounted for all the captures.

answer Qa4#duh