1.Nxe6!
If 1.axb4 at once, 1... Ng3 2.Qg4 Nxf1 3.Rxf1 Nxd3 4.cxd3 and White has nothing to show for the material deficit
1...fxe6
2.axb4Ng3
3.Bg6+
The difference. Now Black's c5 knight has nothing to capture on d3
3...Kd7
4.Qg4Nxe2+
4... Nxf1 is met by 5.Bxc5 and if 5... dxc5 6.Rd1+ Bd5 7.Rxd5+
5.Qxe2Ne4
Black cannot keep his extra piece and his king is horribly placed in the centre.
6.Bd4Nf6
7.Rfe1e5
8.fxe5dxe5
9.Bxe5Qb6+
10.Kh1Bd6
11.Rad1Nd5
12.Be4Rhe8
13.Bxd5Kc7
14.Qc4+
And Black resigns
Christiansen-Reshevsky (1977)