Chess puzzle (Checkmate)
Opening: Nimzowitsch_Defense, Nimzowitsch_Defense_Kennedy_Variation
Moves: 1. e4 e5 2. d4 Nc6 3. d5 Nce7 4. Nf3 d6 5. Bg5 h6 6. Bh4 f5 7. exf5 Bxf5 8.
Bb5+ Bd7 9. Bxd7+ Qxd7 10. O-O g5 11. Bg3 Nf6 12. c4 O-O-O 13. Nc3 Rg8 14. c5
dxc5 15. Nxe5 Qf5 16. Qa4 Kb8 17. Nb5 a6 18. Nxc7 Kxc7 19. Nc4+ Kc8 *
Position (FEN): 2kr1br1/1p2n3/p4n1p/2pP1qp1/Q1N5/6B1/PP3PPP/R4RK1 w - - 2 20
White to move.
Themes:  Middlegame Mate in 1 
Puzzle rating: 1127
Best move: Nb6#