xombie: The final tactic is if 43. fxe3 then 43 .. Rc2 wins the B. But it's very interesting that black went kingside after causing paralysis.
Here are some comments from the book.
After move 21 ... Rc2!.
"The rook is not going to go on the rampage, capturing material to left and right, but its hypnotic glance will spread confusion in the enemy ranks. White's forces will have to stand passively by as the rook induces slow paralysis".
"22. Nxe4 (last move, Black could have won two minor pieces for a rook by 21 .. Rxc1 and 22 .. Nxd2 but decided that he could get more by the occupation of the seventh rank. Stahlberg's nerves give way and he decides to remove the dangerous knight) 22 .. dxe4 23. a3 h5 (now he comes in with a kingside attack) 24. d5 R8c4 25 Rd1 exd5 26. Bd2 Qf6 27. Rab1 h4 28. Qa4 Qf5 29. Qxa7 Bf8."
"This lets White exchange queens and so prolong the game, whereas 29 ... Bg5 would allow Black to decide matters by a direct attack on the king. There's no accounting for tastes, and in the ending the Leningrad grandmaster quietly realised his advantage and forced resignation on move 42".