Helpmate in 5

There are two mate positions one might envisage: bKb1, bNa1, bBc2, bRc1, bRb2, & wNc3; or bKb1, bNa1, bBa2, bRc1, bRb2, & wNa3. But the latter is impossible — it requires clearing the wK from the first two ranks, and there’s simply no time to do that and manoeuvre the knight to a3.

The first setup, though viable, still appears ambiguous, with multiple ways for the wN to reach c3 or the bB to arrive on c2. Remarkably, however, it is once again the quiet wit of the white king on h1 that ordains a single, exquisitely exact path to the goal.

Consider the following sample line: 1.Na1 Na6 2.Ba4 Nc5 3.Rb2 Ne4. At this point, Black may wish to continue with Rc1, then Bc2, allowing White to finish with Nc3# — but the plan never unfolds, as Rc1 inadvertently mates the white king instead. This points to the need to route the wN to c3 via e2, so that the wK is granted a vital hideaway after Black’s Rc1. Accordingly, the knight must follow the c6–d4–e2 path to reach its final square, which in turn requires that the bishop on c6 be moved first:

1.Ba4 Nc6 (naturally, 1.Be4 Nc6 2.Na1 Nd4 3.Rb2+, etc., does not permit the knight to reach e2 in time — hence the sequence must begin by breaking the B+R battery on the c6–h1 diagonal) 2.Na1 Nd4 3.Rb2 Ne2 4.Rc1+ Kh2 5.Bc2 Nc3#, model mate. The wK steps into a pin with Kh2; the bB releases it with Bc2. Pure artistry!