Key: 1.Sf1! (thr. 2.Sg3#) Se4 2.Kg7(zz) d4 3.Sd3 (thr. 4.Sf4#) cxd3 4.Bxe6 (thr. 5.Bf7#) Sd6/g5 5.Sg3# 2...f4 3.Bb1(zz) d4 4.Bxe4 any 5.Bg6# 3...c3 4.Sd3 any 5.Sxf4#.
Three model mates delivered by three different pieces
The key provides a threat that forces the bS to e4, removing it from the potential defensive squares of d7 or d3. White's second tempo move with the king has the following motivation: he maintains his guard on g6 and h6 while preventing the knight from reaching g5. This places black in zugzwang, leaving him with two line-opening moves, d4 and f4.. If 2…d4, (a2-g8 diagonal is opened), white will take advantage by sacrificing his knight on d3 in order to try to mate with the B on f7. Black can defend against this, but then falls prey to the initial threat of Sg3#. 2…f4 is black's only alternative, to which white responds again putting black in zugzwang (black won't be able to guard both d3 and e4; each of his options lead to a different mate).
Comments:
Mit 1.Sf1! (droht 2.Sg3 matt) wird der schwarze Springer an die Deckung von g3 gebunden 1…Se4, um anschliessend durch 2.Kg7 Zugzwang herbeizuführen – und: “Der weisse Läufer macht auf verschiedenen Wegen das Rennen” (P. Heyl, Eisenach) … “Hier musste man überlegen, in welcher Reihenfolge die weissen Akteure ins Spiel gebracht werden müssen” (J. Schottenhamel, Ebersbach), und J. Selbmann (Annaberg-Buchholz) empand das Problem als “ziemlich variantenreich für einen Fünfzüger1”.
