White needs to develop his play on the queenside. If he begins the preparation for the advance of the b-pawn with the move a2-a3, then after b2-b4 he will need further preparation of the advance b4-b5 with the help of the a-pawn, and will have to spend additional time defending b4. Foreseeing this, White chose...

Played in one move, and winning a precious tempo.

Under cover of the powerfully-entrenched knight, White easily demolishes the black defences.

Black resigned.