Intending b4-b5 to open a new front on the queenside.

1...a6 seems preferable, avoiding a weakness on a7, although after 2.a4 Rd6 3.b5 a5 4.Bg4 Rf7 5.Rc1! Bd7 6.Qa3! Qe7 7.Rc7 White keeps strong pressure.

In view of the mating net, Black resigned.

Preparing h4-h5 with a new kingside front.

In view of the threat 4 Bh3, Black had to weaken the light squares.

Sending more pieces to the kingside, where Black can't defend himself easily due to the lack of space.

This intermediate move leaves Black unable to defend both flanks. There followed:

with the decisive threat of 19 Rg7+.