zydeco: Petrosian had a weak tournament but for some reason was able to play like himself against Najdorf.
Najdorf plays prematurely for his central break with 12.e5. It looks good but black ends up with a solid position, control over e5, and a lasting kingside initiative.
At move 18, Petrosian comments: "The present game is extremely instructive in that White, while not making one visible error, and going along all through simply with good moves, soon found himself in a position without prospects. I think this is a good example to demonstrate the importance, in complex modern systems, of creating a sharp strategic picture of the struggle and taking tactical elements into consideration."
Petrosian thought he was close to a quick win when he played 29....Qf5 but missed Najdorf's cute trick with 30.Bxg5 -- based on the idea that black has just cut off the escape squares for his own bishop.
After this exchange, black's initiative is basically gone, but Petrosian keeps grinding away.
Petrosian thought white had a fairly easy draw with 42.Re4. 64.bxa3 was the losing move. White could have just held a draw with 64.b3.