Mate in 3

The knight is currently doing nothing, but if it moves a check at b8 is a possibility, so 1.Sd8 is a natural move for the solver to try, putting the knight within range of two potential mating squares. The quiet threat is the Nowotny 2.f3 with threats 3.Rxd3 and 3.Sxc6 (2...Qc4+ 3.R3xc4). Black can defend by moving to d5, when bishop and queen interfere with each other, allowing the interfering piece to be drawn away from its vital guard. 1...Bd5 2.R3c4+ Bxc4 3.Sxc6; 1...Qd5 2.Sxc6+ Qxd5 3.R3c4. This idea is known as a Wurzburg-Plachutta, and the rooks display a similar pair of variations. 1...Rhe3 2.Be5+ Rxe5 3.Rxd3; 1...Ree3 2.Rxd3+ Rxd3 3.Be5. There is one by-play variation 1...Qe6 2.Se6+ Rxe6 3.R3c4.

Jacob Hoover: White threatens the Nowotny interference 2 f3. There are four thematic defenses to the key, in two pairs of Wurzburg-Plachutta interferences.