Nimzo-Indian Defense: Classical Variation

The move d4 is commonly played by White in the opening because it allows the central pawns to control key squares on the board. It also opens up lines of development for the queen and the light-squared bishop. By playing d4, White is asserting control over the center of the board and preparing to launch an attack on Black's position. This move can lead to a variety of opening variations, each with their own strategic implications and tactical opportunities.

The move Nf6 by Black is a common response to White's d4, as it immediately puts pressure on the central pawn. By developing the knight, Black is also preparing to control the e4 square with a pawn, which would give them a position of strength in the center. Additionally, the knight on f6 provides protection for the king and can act as a defender for Black's pawns and pieces. Depending on White's response, the Nf6 move can be a flexible starting point for a variety of different opening lines.

The move c4 by White is commonly known as the Queen's Gambit, as it offers Black a pawn in exchange for control of the center. By advancing the c-pawn, White is also preparing to develop the queen's knight and bishop to active positions. The move can also create a potential attack against Black's d5 pawn, which may need to be defended by additional pieces or pawns. Additionally, the c4 move can help to limit the mobility of Black's bishop on f5 and provides a strong foundation for future moves in the opening.

In the Nimzo-Indian Defense: Classical Variation, Black often plays e6 after White's c4 move. This move is aimed at controlling the d5 square and preventing White from establishing a pawn there. By playing e6, Black also prepares to develop their light-squared bishop to a strong diagonal on b7 or c6. Additionally, the pawn on e6 reinforces Black's pawn on d5, making it more difficult for White to attack it directly. The e6 move can also limit the scope of White's light-squared bishop, which typically develops to c4 or b5 in this opening.

After the moves 1. d4 Nf6 2. c4 e6, White often plays Nc3. This move develops the knight to a central square and supports the pawn on d4. The Nc3 move also prepares to control the d5 square and potentially put pressure on Black's position. By developing a knight to c3, White is also able to castle quickly and efficiently, reinforcing their king while also freeing up the rook for potential offensive or defensive maneuvers. Additionally, the Nc3 move enables White to be more flexible in the opening, making it easier to respond to Black's moves and adjust their strategy as the game progresses.

After the moves 1. d4 Nf6 2. c4 e6 3. Nc3, Black often plays Bb4. This move pins the knight on c3, rendering it temporarily unable to move without losing material. The Bb4 move also attacks the pawn on c4, putting pressure on White's position and potentially forcing them to make defensive maneuvers. Additionally, the bishop on b4 supports Black's control of the center of the board and increases their development options. Lastly, the bishop on b4 may also be used to trade off White's bishop on c1, which can be an important strategic objective in some variations.

In the Nimzo-Indian Defense: Classical Variation, White often plays Qc2 after Black's Bb4 move. This move gives the queen greater mobility and prepares the way for castling on the king side. The Qc2 move also defends the pawn on c4 and prepares to put pressure on Black's pawn on d5. Additionally, the queen on c2 can support an attack on Black's king side or be moved to the b1-h7 diagonal to target Black's pawn on h7. Finally, by playing Qc2, White can also exert indirect control over the e4 square, potentially limiting Black's options for pawn and piece development.