White to play and mate in two moves. (White moves, Black moves, White then checkmates.) There is only one move White can make which will allow certain checkmate of Black in its next move, so the puzzle is finding that first move. That first move can involve any legal move, including checking the Black King or taking a Black piece. When White’s first move, (the “Key”), is discovered, White in its next move can checkmate Black in 6 different ways, (with a further optional way), depending on where Black moves.

Black

White
Composed by Mark Avery.

The solution is below.

Do you think the key move is:
White’s knight to f6? No, because Black’s queen moves to g7, checking White’s king.

The Solution: You will have noticed that Black is ready to check White’s king with the queen or the bishop, making it difficult for White to prepare a strong strategy. White’s bishop is pinning the black queen to prevent it doing more damage. The solution requires freeing the black queen. The key move is: knight to e7.

If Black’s queen moves to . . .
d5 to check White’s king, the knight takes it. Checkmate.
g6, White’s knight takes it. Checkmate.
e7 to take the knight, White’s bishop takes the knight on e5. Checkmate.
f6 or g7, the rook moves to g5. Checkmate.
f5 or takes the pawn on g4, White’s knight moves to f5. Checkmate.
anywhere else, White’s knight moves to f5.

If Black’s bishop . . .
takes the pawn to check White’s king, the Knight moves to f5. Checkmate.

If Black’s rook . . .
moves to b5, White’s queen takes the bishop on f2. Checkmate.

For any other move black makes, White’s knight can checkmate with f5 or g6.

More chess problems:

The Straitjacket. Easy.
The Dog’s Collar. Medium.
Wuthering Heights. Difficult.
The Harridan. Difficult.
Fiddler’s Elbow. Difficult.
Laurel & Hardy. Two puzzles with a surprise. ‘Laurel’ is easy; ‘Hardy’ is difficult.
(Try also the blog, ‘If God played chess’ and answer the questions posed.)