With a sound extra pawn and the black king stranded in the centre, the rest is easy.

Preparing ...Nb6 with an attack on the weak c4-pawn.

Preparing ...b7-b5.

5.c5 Bb3 6.Nb6 Nxb6 7.axb6 a5 White ends up with a bad pawn structure.

The c-pawn is gone, but the c4-square remains weak.

At first sight this passed pawn doesn't seem too powerful, but it will soon be.

Fighting against the blockade on c3. The game continued:

Black has a decisive advantage.

A strong exchange sacrifice that ruins the black pawn structure.