1.Nxd4!Nxd4
2.c4+Ke5
3.f4+Kf5
Otherwise Black just remains a pawn down
4.Kxd4Bxf4
5.Bxf4Kxf4
6.b4!
Now Black could have lengthened the game with 6... h5, though White should win the resulting queen and pawn endgame after 7.Kd5 Ke3 8.c5 Kf2 9.Ke6
6...Kf5
7.Kd5Kf6
8.a4Ke7
9.a5Kd7
10.g4Ke7
11.a6!
And Black resigned
Isaev-Gordon (1988-89) World Correspondence Championship