Is this Theory ?
How deep is modern chess opening theory ?
"Is this theory" ? We hear this a lot.
Let's take a popular opening, the sicilian Najdorf (played by Garry Kasparov and Maxime Vachier-Lagrave amongst many others...)
Now there are thousands of variations but how deep is the "main" line ?
Let's focus on 6 Be3 which has the standard plan Qd2 and 0-0-0, a very principled approach.
Let's say we explore the main line according to modern opening theory. I.e for each side, I select the most common, or most played move played by White and Black respectively. in other words, the central branch in the 6 Be3 Variations Tree, within the Sicilian Najdorf Forest
(the trees could represent 6 Be3, 6 Bg5, 6 Be2, 6 a4, 6 h3,etc,etc in the Najdorf Forest)
"Is this still theory" ? yes absolutely. Position after 14..a5 (including Anand in 2006!) has been seen many times in official games, including grandmaster games. We are still within the opening variation tree.
Shall we continue our journey ?
Position after 18 Bh3. known theory.
Here's the position after 26..g6, following the most played moves.
I would say that this position is known and potentially studied by Sicilian Najdorf players. So theory would end around 26th or 27th move ( very few examples beyond). This is theory.
One might even consider what happens after 27 Kb1 d4!? with a complex position. 27 Qf7!? is interesting. You also have cases where you transpose, i.e the move order differs but you converge back into a known position,
Of course it would be necessary to study branches, i.e there are several lines where either White or Black deviates. Time-consuming but you cannot only focus on the main line.
I am showing below one important game for this variation played in Wijk Aan Zee, a top tournament where I assume players prepared at least until move 26. White won.
and here is Anand's game featuring 16 Nbd4 by Sergey Karjakin
