King's Indian Defense: Orthodox Variation, Classical System, Traditional Line

This aggressive chess opening leads to complex middlegame positions and is favored by many top-level players.

The opening is characterized by a pawn structure in the center, with Black aiming to counterattack on the kingside. It is a highly flexible and dynamic opening, allowing both players to choose from a variety of plans and pawn structures. The main idea for Black is to play for the e5 pawn break, which can lead to sharp tactical battles and imbalances in the position.

White's setup is solid and classical, with the aim of controlling the center and preparing for a potential kingside attack. The knight on e1 is a key feature of this variation, as it allows White to support the f3 pawn and prepare for the eventual f4 pawn break. This opening has been played by many top-level players, including former World Champions Garry Kasparov and Anatoly Karpov.

Black's main idea is to play for the f5 pawn break, which can lead to sharp tactical battles and imbalances in the position. The knight on e7 is well-placed to support this pawn break, and the bishop on g7 is a strong piece, exerting pressure on the long diagonal.

Overall, this opening is a rich and complex choice that can lead to exciting and challenging middlegame positions for both players.