Mate in 3

A number of three-move themes employ a similar structure. White has a try threatening an immediate mate, to which a black piece has a successful defence. After the key a black piece is decoyed, in such a way that when White continues with his original threat the successful defence is no longer available but is replaced by an unsuccessful defence. In the Hamburg variant the same piece provides both the successful and unsuccessful defences while a different piece is decoyed. Here the try is 1.g8S? threat 2.Sxe7, met by 1...Bh4! The key 1.Rh8 clears the rank to threaten 2.g8Q and 3.Qe8. Black’s only defence involves a line clearance to allow the queen to reach g4. 1...Rh4. White continues 2.g8S threat 3.Sxe7, and the only defence is 2...Bxc5, the selfblock freeing the knight for 3.Sd8. A clever point is that 1.Rd8? fails because d8 is no longer available for the knight.