L Kubbel, Shakmaty v SSSR 1938
White to play and mate in four
The key is the splendid 1.Qd7!, giving the BK two flights on d5 and c5. The threat is 2.Nc4+ or 2.Ne4+, followed in each case by symmetrical mates with 3.Qd6+ and mate on either b6 or f6. Similar symmetrical mates follow after the king flights to c5 and e5, whilst 1...Kd3 provides a third, unthematic variation.