With this move, Black gets rid of an ‘unnecessary’ piece, and not only strengthens his blockading knight, but the whole complex of dark squares. It is important that now the white Bf3 becomes a bad piece, blocked in by its own d5-pawn.

A serious positional mistake, after which White is left with a bad bishop against a beautiful knight. It was essential to decline the exchange, and retreat the bishop to d2 or e3 – in this case, White would retain counterplay, since then Black does not get a free hand for major-piece play on the dark squares.

After an exchange of dark-squared bishops, outposts appear on e5, e3 and g5 – Black happily exploits them.

Now, the blockade is lifted, and Black’s advantage disappears with it.

Objectively, White’s position is somewhat better. As is well-known, the queen is a poor blockader. In addition, the white pieces are already on strong squares. The direct idea of transferring the knight from f6 to d6 either fails tactically, or is met by a basic refutation in the form of the move Bc2-a4 and the exchange of the knight on e8, with an obvious advantage to White.

Black goes for the sacrifice, to exchange some major pieces.

An important move. Black gives up a pawn, but exchanges all the rooks.

White has an extra protected passed pawn, but the position is a draw.

Unlike the queen, the knight is an excellent blockader! It fulfils its function of keeping the white king out excellently.

Draw agreed.

White has the advantage, thanks to his extra space. But how great is this advantage? Black’s plan is to strengthen the e5- pawn if necessary with ...f7-f6, bring his Ra8 to the centre (probably with the help of exchanges on the d-file) and include his light-squared bishop in the game via c8. If he succeeds in doing this, White will have few chances of a break on the kingside. By exploiting a tactical motif, White finds a way to change the position in his favour: