Intending ...b5-b4 to weaken the a1-h8 diagonal for the bishop, in particular the d4-square.

Now the bishop is doing a great job in helping his colleague to put pressure on g2.

And subsequently won the game.

Giving up the bishop pair in exchange for another advantage: a weak enemy pawn on d6.

Or 2...Qxh4 3.gxh4 and the d6-pawn falls right away.

After 4...Nc6 5.Bc7 that pawn is also doomed.

White wins a pawn with a decisive advantage.

Black "messes up" the game before White manages to consolidate, with a long-term advantage thanks to the bishop pair.

If 3.Nb1, preparing 4 f3, then 3...f5! with the idea of 4.f3 Nxg3 5.Nxg3 f4+ etc.