As with most of Speckmann's problems, this too features a lightweight setting but is highly instructive nevertheless. It is White to play and mate in 4. What is the key move?
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1. Bb3 Bh7 - Black's only defense against Bc2 and the threat of BxB is to hide the bishop on h7 and push f5 next. And that's exactly what they do. White to play; how do you continue?