This concept was first mentioned in Lipnitsky’s “Questions of Modern Chess Theory”. Fischer mentioned it again in his famous article “A Bust to the King’s Gambit”. So what is it all about?
Let’s look at the starting position of the Classical Sicilian:
There is one striking feature and that is that the black knight on c6 cannot move to d7 anymore. White can try to exploit this with Bg5 (Rauzer), which is still the main line today:
If black on the other hand plays a “high-class waiting move” like 5… a6 (Najdorf), then he keeps the option of reacting to Bg5 with Nbd7.
Where else does this concept apply?
1. d6 in the King’s Gambit (Fischer)
2. Be7 in the QGD
Black waits for the white knight to show up on f3, so the Exchange-Variation loses a lot of it’s bite.
3. Be7 in the French Tarrasch (Morozevich)
By playing like this black keeps the option to play either Nf6 or c5 next move, thereby eliminating the f4-line against Nf6 and some of the critical lines against c5.
There is also this funny line which has been played by Moro also:
4. a6 in the Slav (Chebanenko)
5. The latest fashion in the Najdorf for white is to react to a6 with a high-class waiting move of his own:
6. One could even call this a high-class waiting move: