When Black is forced to place a rook in such a position to avoid mate, the correctness of the sacrifice becomes obvious.

Because there is no forced win, White simply strengthens the centralisation of his pieces, so as to be prepared to create threats on the kingside, and also support the advance of his passed pawns.

With piece support, the passed pawns decide the game.

The Bf3 is the most important piece, and, given the weakening of the central light squares, is fully worth a rook.

Of course, Black could get excellent counterplay with 12...Bb7 or 12...Nc6, but the move played in the game is stronger.

White should not open lines, but, on the contrary, try to keep the game as closed as possible. Therefore, 16.f5 was essential, although Black’s initiative is very strong all the same.

The white king has lost its only place of refuge, and now Black quietly brings up the rest of his pieces, to prepare the decisive blow.

And Black won.

Usually in such structures, Black puts his bishop on a4, and if possible supports it by ...b7-b5, cementing the queenside. This is exactly what Black would have done here if White had dawdled.

At the cost of a pawn, White activates his bishop, and it goes from being the most passive of his pieces to the most active.