Longest mate in King, Queen and Knight versus King endgame

Mate in 9

Also available in PGN notation.

White to move
Mate in 9 with Kg2, Kh2, Ne2, Nf3, Nh3, Qa1, Qa2, Qb2, Qb3, Qb4, Qb8, Qc1+, Qc2+, Qd1, Qd3, Qe1, Qe4+, Qf1, Qf5, Qg6+ and Qh7. Worse are Qb5+, Qb6+ and Qb7+ which throw away the win.
1. Ne2
White mates in 8 after Kc5. Worse are Kc7, Kd5 and Kd6 when White mates in 7, and Kd7 when White mates in 6.
1... Kc5
Mate in 8 with Kg1, Kg2, Kh2, Nc3, Nd4, Nf4, Qa1, Qa2, Qb2, Qb3, Qb7, Qb8, Qc1+, Qc2+, Qd1, Qd3, Qe4, Qf5+, Qg1+ and Qg6. Worse are Nc1, Ng3, Qe1, Qf1 and Qh7 with mate in 9, Ng1 with mate in 10, and Qb4+, Qb5+ and Qb6+ which throw away the win.
2. Qf5+
White mates in 7 after Kc6. Worse are Kb6, Kc4 and Kd6 when White mates in 6, and Kb4 when White mates in 5.
2... Kc6
Mate in 7 with Kg1, Kg2, Kh2, Nc3, Nd4+, Nf4, Qa5, Qe5 and Qg5. Worse are Nc1, Ng3, Qc2+, Qc8+, Qd3, Qe4+, Qe6+, Qf2, Qf3+, Qf4, Qf6+, Qf7, Qf8, Qg4, Qg6+ and Qh5 with mate in 8, Ng1, Qb1, Qf1, Qh3 and Qh7 with mate in 9, and Qb5+, Qc5+, Qd5+ and Qd7+ which throw away the win.
3. Nc3
White mates in 6 after Kd6. Worse are Kb6, Kb7 and Kc7 when White mates in 5.
3... Kd6
Mate in 6 with Qd5+. Worse are Kg1, Kg2, Kh2, Na4, Ne4+, Qb5, Qe4, Qg5 and Qh5 with mate in 7, Na2, Nb1, Nb5+, Nd1, Nd5, Ne2, Qa5, Qb1, Qc2, Qc8, Qd3+, Qf1, Qf2, Qf3, Qf4+, Qf6+, Qf7, Qf8+, Qg4, Qg6+, Qh3 and Qh7 with mate in 8, and Qc5+, Qd7+, Qe5+ and Qe6+ which throw away the win.
4. Qd5+
White mates in 5 after Kc7 and Ke7.
4... Ke7
Mate in 5 with Ne4. Worse are Qc6 with mate in 6, Kg1, Kg2, Kh2, Na4, Nb5, Nd1, Ne2, Qa8, Qb5, Qb7+, Qc4, Qc5+, Qe4+, Qe5+, Qf3, Qf5, Qg2, Qg5+ and Qh5 with mate in 7, Na2, Nb1, Qa2, Qa5, Qb3, Qd1, Qd2, Qd3, Qd4 and Qg8 with mate in 8, and Qd6+, Qd7+, Qd8+, Qe6+ and Qf7+ which throw away the win.
5. Ne4
White mates in 4 after Ke8. Worse is Kf8 when White mates in 3.
5... Ke8
Mate in 4 with Qb7 and Qe6+. Worse are Nc5, Ng5 and Qd6 with mate in 5, Kg1, Kg2, Kh2, Nc3, Nd2, Nd6+, Nf2, Nf6+, Ng3, Qb5+, Qc5, Qc6+, Qd1, Qd2, Qd3, Qd4, Qe5+, Qf5, Qg5, Qg8+ and Qh5+ with mate in 6, Qa2, Qa5, Qa8+, Qb3 and Qc4 with mate in 7, and Qd7+, Qd8+ and Qf7+ which throw away the win.
6. Qb7
White mates in 3 after Kd8 and Kf8.
6... Kd8
Mate in 3 with Nc5, Ng5, Qf7 and Qg7. Worse are Kg1, Kg2, Kh2, Nc3, Ng3 and Qh7 with mate in 4, Nd2, Nf2, Qa7 and Qc6 with mate in 5, Qa6, Qb2, Qb4, Qb5, Qb6+, Qb8+ and Qd5+ with mate in 6, Qa8+, Qb1 and Qb3 with mate in 7, and Nd6, Nf6, Qc7+, Qc8+, Qd7+ and Qe7+ which throw away the win.
7. Ng5
White mates in 2 after Ke8.
7... Ke8
Mate in 2 with Qc7. Worse are Qf7+ with mate in 3, Kg1, Kg2, Kh2, Ne4, Nf3, Nf7, Nh3, Nh7, Qa7, Qg7 and Qh7 with mate in 4, Qb5+, Qc6+, Qc8+ and Qd5 with mate in 5, Qa6, Qb2, Qb3, Qb4 and Qb6 with mate in 6, Qa8+, Qb1, Qb8+, Qe4+, Qf3 and Qg2 with mate in 7, and Ne6, Qd7+ and Qe7+ which throw away the win.
8. Qc7
White mates in 1 after Kf8.
8... Kf8
Mate in 1 with Qf7#. Worse are Kg1, Kg2, Kh2, Ne4, Ne6+, Nf3, Nh3, Nh7+, Qa7, Qb7, Qd7, Qe5 and Qh7 with mate in 3, Qc5+, Qd6+ and Qd8+ with mate in 4, Qb6, Qc1, Qc2, Qc3, Qc4, Qc6 and Qc8+ with mate in 5, Qf4+ with mate in 6, Nf7, Qa5, Qb8+, Qg3 and Qh2 with mate in 7, and Qe7+ and Qg7+ which throw away the win.
9. Qf7#
Checkmate.
1-0


An endgame analysis by Joe Leslie-Hurd on 16 February 2005.