# Pawn Promotion Endgame Problem-White to move and mate in 1

So I have not been this interested in chess for a very long time indeed. This problem was posed to me by someone who has recently become experienced in chess and also participated in a chess tournament, in which he did fairly well considering his level of experience.

``````[Title "White to move and mate in 1"]
[FEN "8/kPR5/5Q2/8/8/8/6B1/4K3 w - - 0 1"]
``````

From my own deductions, the only possible way in which to even begin to solve the problem is with the move b7 to b8. However, I have yet to figure out how promoting the pawn can have an effect on the eventual outcome of the scenario, seeing as the black king can simply take whichever piece I decide to transform the pawn into.

The last hint I was given, by the person who posed to question to me, was that the relationship between the piece into which the pawn is transformed and the black king is paramount to the solution.

Please help me. All the chess engines I have tried using after an absurd amount of time, trying to figure it out by myself, and doing it with the help of others have failed me.

• This is a joke problem. Jul 6 '15 at 17:53

It's probably a trick problem with a promotion to a black knight.

Such promotions to the wrong colour are not allowed, and never were. In the official rules it is now specifically pointed out that the new piece has to have the same colour as the promoted pawn.

FIDE's laws of chess, Article 3.7 e:

When a pawn reaches the rank furthest from its starting position it must be exchanged as part of the same move on the same square for a new queen, rook, bishop or knight of the same colour. The player’s choice is not restricted to pieces that have been captured previously. This exchange of a pawn for another piece is called ‘promotion’ and the effect of the new piece is immediate.

Mate in one move is impossible here, but there is a forced mate in two.

You're right that the solution begins with a pawn promotion; you just need to continue playing out the line. Promote to any piece - it doesn't matter which - and the only legal move for black is to capture the new piece. Then simply drop your queen to D8 (or B6), and it's mate in two.

``````[FEN "8/kPR5/5Q2/8/8/8/6B1/4K3 w - - 0 1"]

1.b8=N+ Kxb8 2.Qd8# 1-0 (2.Qb6# 1-0)
``````
• There's also a mate in 2 starting with 1.Qa1+ (then either 1...Kb6 2.b8Q# or 1...Kb8 2.Rc8#). Jan 6 '15 at 12:47

At first I thought it could be the typical "board is not oriented as you are asuming" trick, but it doesn't seem to work;

Option 1: The white pawn is actually in the g2 square. But it isn't enough, because after, for example, g4+, then Kg1 saves the king.

Option 2: The white pawn is in the g7 square; but after, for example, Qf8+, Kh7 saves the king again. Besides, in this case the board would be misplaced (white square on the left-down corner of the players).

Because of the pawn placement there aren't any en pasant tricks etiher. So, all in all, I agree with the suggestions that the only solution is false, based on promoting to a black piece.

Option 3; white pawn is in b2. But again, after Qe4+, then Ka2 saves the black king again. And in this case, again, we have the problem of the white square on the right side.

As the first answer above indicates, this is a trick question and can be found on youtube. The question is so posed that the pawn can promote to ANY piece, not restricted to color, so 1..., b8(Black N) is mate. But this is illegal, so the problem is meaningless.

This is a trick question because the only way to mate in one is to promote the pawn to a black knight, this stops the king from taking this space. While it is now illegal this problem was designed by a chess grand master he created this problem to make it an official rule that you can only promote to the same color as the pawn. This problem was relevant at the time because you could promote to any color but there was never a situation in which doing so would benefit you. The problem is a part of chess history and is the very example that created the promotion rule.

Long ago question that is perhaps more interesting than was realised.

Give the problem to a human,and the reaction is, "This has no solution, so the question is only worth asking if there is some amusing trick answer. What could the trick be?" Computers cannot do this, at least not yet, without being given a list of possible tricks.

Humans, therefore, think much more flexibly and creatively than computers. Outside the box,if you will excuse the cliche.