An unexpected advance that drastically alters the balance of the position.

1...b6 2.Ba4! White is soon able to land a knight on c6
1...cxb4 2.axb4 Bxb4? 3.Qxf6 Bxc3 4.Ng4 h5 5.Nh6+ Kh7 6.Bxg6+ with a decisive attack.

White has emerged with a mobile pawn majority on the queenside.

Weakening the a2-g8 diagonal, but it was not easy to find a constructive plan.

White later realized his material advantage.

This exchange sacrifice completely changes the logic of the position. Now the threat is 2 Bf4.

This lets the white knight occupy the newly created post on e5.

2...Nd7 3.Bxh6 Re8 was preferable, when 4.Bd3 Nb6 5.Ne5 Nxd5 6.Be4 keeps a clear initiative.

Now d5-d6 is inevitable.

Black resigned.