How far do chess players have to see ahead? To a large extent it depends on the position. In some it’s just impossible and unnecessary to calculate whilst others require great precision in one’s tactical operations.
There’s also a issue with a player’s particular abilities, some players just know that particular positions are good whereas others need to work through a lot of variations before they know what’s going on. Viktor Korchnoi was reputed to be someone who needed to calculate a lot but I suspect he learned to manage with rather less on his run up to the 1978 World Championship match he had with Anatoly Karpov. After being a life long time trouble addict, Korchnoi suddenly started to pace himself rather better. And at that time he was probably just as strong as Karpov.
Are all brilliant combinations calculated through to the end? The winners would probably like us to think so but I suspect they often don’t remember things that well or confuse what they saw during the game with what emerged during the post mortem. In any case I’m not sure it should matter that much, a brilliancy is no less brilliant because some of the moves were played on intuition.
The following game, known as the Polish Immortal, is one in which it looks almost impossible to see the whole attack from the start. Even though Najdorf had brilliant calculating ability I suspect that initially it was his intuition that told him the position after 12…Qh5 had to be good for Black. Perhaps at that stage he saw through to 15…e5, sensing that the attack had to be very strong and then on 19.Kf3 saw through to mate or winning White’s queen.
It would also be interesting to know what Glucksberg saw, especially when he played 9.Ng5, apparently just missing Black’s 9…Bxh2+. I suspect that he intended this as a trap as it’s far from easy for Black to free his bishop after 11.f4.