White has excellently-coordinated pieces, a far advanced passed pawn, and a lovely knight in the centre. With the help of...

a mating net is created around the black king. The threat of 31.Qf7+ and 32.Qf8 is unstoppable, and so Black resigned. On 30...Qxb6, the game ends by force after 31.Qf7+ Kd8 32.Qf8+ Kc7 33.Qxe7+ Kb8 34.Nd7+.

The black king is boxed in on all sides by its own pieces, and this makes possible a tactical blow, which White had undoubtedly seen in advance:

Whether the queen is taken or not, there is no defence against a deadly knight check on g6.

Having extra material, it is better to defend the ‘base’ pawn, to win the game without undue adventures.

In the pawn endgame after 37...Rc4 38.Rxc4 dxc4 39.Kf1, the king is in the square, and the passed a-pawn brings White victory.

Black’s bishop on g5 is hanging, as is White’s Re4. But the black king turns out to be surrounded by white pieces when it takes on e4.

And now the key move of the variation:

Black resigned, because there is a threat of 32.Bd2#, and on 31...e4 there follows 32.Nh3#.

Black has an extra piece, but the pawn on a7 is very dangerous, and is impossible to capture with checks. For example, after 53...Qc1+ 54.Kh2! Nf1+ (54...Qb2+ 55.Qg2!) 55.Kg2 Ne3+ 56.Kf2 Qd2+ 57.Kg1 Qe1+ 58.Kh2 Nf1+ 59.Kg2 Ne3+ 60.Kh2 Qd2+ 61.Kg1 Qc1+ 62.Kf2 Qd2+ 63.Kg1, the game ends in a draw.