White to Move – What is Shortest Number of Moves in which White May Mate?

DIAGRAM CCKM-P6cckmp6

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This problem is designed to test the ability to spot

an opportunistic checkmate (the opposing player moves wrong allowing the player to mate)

versus

forced checkmate (the opposing player will be mate regardless how the opposing player moves).

White May Mate in 2 with help from Black:

either 1.Be4 (if Black makes any move or pawn advance other than 1…Qf1+ or 1…Qh1+ (a game deciding blunder because White would simple capture the Queen with the Bishop) then White simply mates with 2.Qxh7#)

or 1.Nxf6 (if Black makes any move or pawn advance other than 1…Qxf6 or 1…Qf1+ then White simply mates with 2.Qxh7#)

White also May Mate in 3 with help from Black:

either 1.Qf7+ Kg6 (Black moves wrong allowing White to mate in 3; Black should have blocked check with 1…Bg7) 2.Be4+ Kxh5 3.g4#

or 1.Qf7+ Kxh5 (Black moves wrong allowing White to mate in 3; Black should have blocked check with 1…Bg7) 2.g4+ Kg6 3.Be4#