An attempt to cover the square f4 against an entry by the black queen. But the knight is badly placed here, because it does not perform any other functions. White’s problems are growing.
Including yet another piece in the attack on the dark squares, decides the game.
29...fxe5 30.Qxg5 e4 31.f6 g6 32.f4 hxg4 33.Be2 gxh3 34.Bh5 Rb2 35.Nh4 Qxf4 36.Qxf4 Bxf4
Unity Chess Club
Paul Keres Vasily Smyslov Bled/Zagreb/Belgrade 1959 Black to move
There is a lack of coordination among the white pieces. Exploiting this, Black creates an object of attack on the queenside:
He should not allow Black to open lines for his rooks; instead, he should prefer 20.bxa5 bxa5 21.Nd4, with chances of equalising.
The pawn stands slightly more actively, taking c4 from the white knight, and opening a path to b6 for the bishop.
24.Nc2 Ra2 25.Nb3 Rc8 26.Ncd4 Bd8! 27.Rxc8 Bxc8 28.Rc1 Bd7 29.Kh1 Qa8 30.Bh4 Bb6 31.Qd1 31...Qa4 32.Be1 h6
33...e5! 34.fxe5 Ng4 35.Be1 dxe5 36.Nf5 Bxf5 37.exf5 Rxg2 38.Rc8+ Kh7 39.d4 Rxh2+ 40.Kg1 Bxd4+