Sacrificing a pawn in order to enter with the bishop on a4 and c2.

The only way to parry the threat of 6...h4.

Black soon won.

To clear the long diagonal for the bishop.

Preferable was 2.Bc5! dxe4 3.Qe2 with unclear play.

With ideas like ...Ne5-d3 and ...N7b6-a4, Black enjoys excellent attacking prospects.

The bishop is transferred to the long diagonal where it will attack Black's queenside.

In the event of 1...Bxe3?! 2.fxe3 Rxc3 3.Bxb7 White would have a huge advantage.

Removing the pawn from the bishop's sight, but now the queenside is weakened.