zydeco: Petrosian says that he chose this line against his better judgment - he was surprised by Fischer's opening choice.
Fischer rejected 16.Bf4 because of 16....f6, although Petrosian had planned 16....Nd7 17.fxe6 Nf6.
On move 20, Petrosian writes: "White's plays is logical while black has long been balancing on an abyss. Fischer, therefore, without long thought, captured the KP, feeling, not without foundation, that the agony of black's army had begun. But I have already stated that in this system [Paulsen's Variation] it is the tactical points of concentration that save black."
If 21.Rxf8 Nxe6
If 23.Rf7+ Kb6 24.Rc8? Bc5+
Fischer played very purposefully and logically in this game, and Petrosian had to be extremely resourceful to draw.