The truth of the matter is that chess players seldom play out a single opening..Since most openings are pretty well known (along with their optimal moves), the

The truth of the matter is that chess players seldom play out a single opening..Since most openings are pretty well known (along with their optimal moves), the beginning part of a chess game is usually spent trying to maneuver your opponent into an opening of your liking (or trick them into thinking you are playing one thing, then switching on them). What starts out looking like the Slav , may end up Queens Indian (as an example), and this makes the 20 moves ahead claim even more ludicrous. There are whole books on (slaying) the dragon variation of the Sicilian defense and the Sicilian is just one option that can result from the first move being e4..of course your opponent can also transpose to a different formation as the game progresses. In the end game where there are relatively few pieces on the board you may be able to plan ahead with more precision, but other than that trying to think 20 moves ahead is not just impractical, it may well be dumb.