Continuing with Fischer - Unzicker, Zurich 1959, Kasparov criticized Fischer's analysis on the diagrammed position. Fischer played 35.Be2, which was awarded '!' by both the 11th and 13th World Champions. Unzicker answered 35...Re7, to which Kasparov assigned '?'. There is a sequence of nice tactical shots hidden in the position.
In his notes Fischer asked, 'How can Black defend the Pawn?', and gave four variations:-
'(a) 35...b4? 36.Ra6 Nxe4 37.Qh4 Qd5 38.Bf3 Qd3 39.Ra7 wins
'(b) 35...Nxe4? 36.Qh6 Re7 37.Qf8 mate
'(c) 35...Qb6 36.Rf7 Ng8 37.Qh4 h6 38.Qg4 Rd8 39.Bxb5! wins
'(d) 35...Rb8 36.Rf7 Ng8 37.Rd7 Qf6 (37...Qxd7 38.Qxe5+ Qg7 39.Qxb8 Qxc3 40.Qxb5) 38.Qe3 Qc6 39.Rd5 when one of Black's hanging Pawns must fall.'
Kasparov repeated Fischer's analysis and then quoted GM Robert Huebner, '"However, Fischer fails to take an important defensive resource into account though tactical and positional reasons suggest to play 35...c4", writes Huebner'.
[FEN "4r2k/R6p/3q1np1/1pp1p1Q1/4P3/1PP5/5PP1/3B2K1 w - - 0 35"]
After continuing to quote Huebner,
"35...c4 36.bxc4 (36.Rf7? cxb3!) 36...Qb6 (36...bxc4? 37.Bxc4 Qd1+ 38.Bf1 Ng8 39.Qh4! h6 40.Qh3) 37.cxb5 Qxa7 38.Qxf6+ Qg7 39.Qc6 Rf8 and, "it is not clear whether the position can be won for White; but at any rate, tremendous work is necessary before he can secure victory."
Kasparov added his own analysis,
In my view, after 40.Qd6!, this task is not so great: tied to the defense of the e-Pawn, Black is unable to halt the victorious march of the b-and c-Pawns. 39...Qe7 is more tenacious, but even then after 40.b6! Kg7 41.b7 Rb8 42.Ba6 with the threat of Qc8 and c4-c5-c6-c7 White should win.
plus a typical gratuitous remark about how much better the players are today:
Nevertheless 35...c4 36.bxc4 Qb6 was the best practical chance (bearing in mind that after 37.cxb5 Black can also consider 37...Nxe4) and in our time, when the level of resistance has increased sharply, any grandmaster would play this without much thought.
Not only would any grandmaster play this without much thought, so would any computer. Mine finds it after a few seconds. Was Huebner's discovery of 35...c4 also due to computer assisted analysis? In deference to the analytical ability of the great German GM, my instinct says 'No!', but I'm not really sure.
After Unzicker's 35...Re7, Fischer won a Pawn with 36.Rxe7 Qxe7 37.Bxb5, and went on to notch the full point in another 30 moves.