The time-trouble phase is over and White resigned.

White wants to entrench his knight on d4, after which he can prepare an attack on the kingside with g3-g4 and f4-f5. The move ...h6-h5 will not bother him, because he can reply simply h2-h3. Of course, White’s plan is hard to implement, but it is potentially possible, and Black cannot afford to relax. Therefore, exploiting a fleeting chance, Black sharply changes the picture, forcing White onto the defensive:

A brilliant decision! Black solves all his problems, which consist of his inactive bishop, blocked by the enemy pawns, and his lack of space. The connected passed pawns created by the sacrifice are joined by the d5-pawn, and form a dangerous avalanche. The pawns have a long way to go to promote, and therefore Black had to realise that the position is fairly closed, and the white knight cannot organise counterplay on the kingside.

By playing 40...b4!?, it was possible to pose White greater problems.

Passive defence on the queenside does not lead to any happiness, and so White seizes the first chance for counterattack, which proves to be the saving resource.

This could also have been delayed until the next move, when the black rook stands on b5, but Black decided not to fight against the inevitable.

Similar positions frequently arise in the Queen’s Indian Defence, and the device used now by White is a typical one:

In this case, the knight jump leads to a gain of material, but sometimes it is played just with the intention of transferring the knight to a5 or e3, or to attack an enemy queen on b6, exploiting tactical motifs as the knight cannot be captured, because the d5-pawn is pinned along both file and diagonal.

And White won.

Black has the advantage of the two bishops and his pieces are actively placed, excellently supporting his pawn duo. Now, there follows a break, which crowns Black’s build-up: