One Pawn vs. the Black Army

[FEN "1n6/Pp1p1p1p/1P1P1P1P/4K3/2p5/p7/rpp1P3/qkb1R3 w - - 0 1"]
1. axb8=N c3 {Black's only hope is stalemate. White, however, sees ways of
giving him some more moves.} 2. Na6 {! Not 2.Nc6?? allowing black to run the
b7 pawn aground along the c-file, sooner than it could on the a-file.} bxa6 3.
b7 a5 4. b8=N {! Same bat square, same bat promotion. Black is continually in
danger of running out of pawn moves, so white feeds them a continual supply of
Knights they must capture.} a4 5. Nc6 dxc6 6. d7 c5 7. d8=N {By now, even the
thickest solver can tell what's going to happen.} c4 8. Ne6 fxe6 9. Kd6 {! The
right square, avoiding any checks from the advancing e6 pawn.} e5 10. f7 e4 11.
f8=N e3 12. Ng6 hxg6 13. h7 g5 14. h8=N g4 15. Ng6 {There are duals in this
one, too: 15. Nf7 g3 16. Ng5 g2 17. Ne4} 15... g3 16. Ne7 g2 17. Nd5 g1=B 18.
Nxc3