Daily chess puzzle: Check Mate # 85(2)

Yesterday, I posted this problem, from Dragoslav Andrić's book Matni Udar, the puzzle book that I am presently working through.

White to play and mate Black

Hartlaub v Walle, Bremen 1923

I gave the solution, as in the book, 1 Re7 Qe7 2 Rf6 gf 3 Nf5 Qe4 4 Qg5+!! 1-0. The book also gives the alternative line 3…Qe6 4 Qf4 Kh8 5 Qh6 1-0).

Alas, something is wrong. Stockfish, the iPad app I use for posting the diagrams, immediately flashed up 1 Nf5! with a +5 assessment; giving only a +2 assessment to 1 Re7, and swinging to a -4 assessment after 2 Rf6?.

Once I saw the assessment, I looked to understand the position after 3…Qe6. It immediately became clear that 4…Rd8! gives Black's king sufficient luft: there is no mate or N fork after 4 Qg4+ Kf8 5 Qg7+ Ke8[].

Instead, better, after 1 Re7 Qe7 is 2 Bf6! gf[] 3 Nf5 so that after 3…Qe4 or 3…Qe6 White plays 4 Qh6 and mates unless Black plays 4…Qf5 5 Rf5, after which White has an easy win in the endgame.

But best of all, simply play 1 Nf5 and after say 1…Nc6 (to defend the Be7 and develop) 2 Qg5 is overwhelming. Black loses a piece after 2…g6 (or, in fact, it is mate in 6, per my engine: 3 Nh6+ Kg7[] 4 Re7! etc).

So the problem isn't cooked, but the solution was, but the spoiler was well hidden.

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