An endgame study from 1906 by Alexei Troitzky.
White to move and win.
Solution:
1.Nd6! a2 2.Nf7+! Kg6!
2...Kg7 3.c8Q a1Q 4.Qh8+ Kxf7 5.Qxa1.Or:2...Kh5 3.c8Q a1Q 4.Qf5+ Kh4 5.Qf4+ Kh3 (5...Kh5 6.Qg5 mate) 6.Ng5+ Kg2 7.Qf2+ Kh1 8.Qh4+ Kg2 (8...Kg1 9.Nf3+ Kg2 10.Qh2 mate) 9.Qh3+ Kg1 10.Nf3 mate.
3.Ne5+ Kf6
Other black moves makes no difference.
4.c8Q a1Q 5.Qf8+
And now not 5...Kxe5 6.Qh8+ or 6.Qg7+ followed by 7.Qxa1.
5...Kg5! 6.Qg7+ Kf5
6...Kf4? 7.Qg4+ Kxe5 8.Qg7+ and 9.Qxa1.
6...Kh5? 7.Qg4+ Kh6 8.Nf7 mate.
7.Qg4+ Kf6 8.Qf4+ Ke6
Or 8...Ke7 9.Qf7+
9.Qf7+ Kd6 10.Qd7+ Kc5 11.Qc6+ Kb4
11...Kd4? 12.Nf3 mate.
12.Nd3+ Kb3 13.Qd5+ Kc2
13...Kc3 14.Qe5+
13...Ka3 14.Qa5+
13...Ka4 14.Qc4+ Ka3 (14...Ka5 15.Qb4+ Ka6 16.Nc5+ Ka7 17.Qb7 mate.) 15.Qb4+ Ka2 16.Qa4+ Kb1 17.Qb3+ Qb2 18.Qxb2 mate.
14.Qc4+ Qc3
14...Kb1 15.Qb3+ Qb2 16.Qxb2 mate.
15.Qa2+ Qb2 16.Qxb2 mate.
