In Fischer vs. Petrosian at Belgrade 1970, GlennGiffen says, 'The other day I read the interview with Kasparov about My Great Predecessors 4 at Chess Cafe. He said that Fischer's first win over Petrosian at the USSR vs. the World team tourney in Belgrade 1970 was the beginning of Fischer's real ascendancy in Soviet eyes. I dug up the game, and played it over, and started wondering why Petrosian would play 17...Kf8 instead of castling.' • What do you think? What was Petrosian so afraid of?