Nimzo-Indian Defense: Classical Variation, Keres Defense

A solid and flexible chess opening for Black, focusing on controlling the center and creating imbalances in pawn structure.

The opening is a popular choice among players of all levels, as it offers a solid and flexible setup for Black. It is characterized by Black's early fianchetto of the light-squared bishop and the exchange of the dark-squared bishop for the knight on c3. This exchange creates a doubled pawn structure for White, which can be both a strength and a weakness.

The main idea behind this opening is to control the center and create imbalances in the pawn structure, which can lead to dynamic play and interesting middlegame positions. Black's pawn breaks with c5 and d5 are typical plans to challenge White's central pawn duo.

White's main plan is to use the doubled c-pawns to control the d5 square and potentially create a passed pawn on the queenside. The queen's placement on c3 also supports a potential e4 pawn break, which can lead to a strong central pawn duo for White.

The Keres Defense, named after the Estonian Grandmaster Paul Keres, is a specific variation within the Classical Variation of the Nimzo-Indian Defense. It involves Black playing an early b6, preparing to fianchetto the light-squared bishop on b7.

This variation is known for its flexibility, as Black can choose between various pawn structures and plans depending on White's play. It is a solid choice for players who enjoy strategic battles and are comfortable playing with imbalances in the position.