Queen's Gambit Declined: Modern Variation, Knight Defense

The opening move 1.d4 is a common choice for White which helps control the center of the board. This move is often the first step towards the development of the queen's bishop and queen's knight. It also allows White to put pressure on Black's d5 pawn. By playing d4, White aims to control more central squares in preparation for an active game.

The move 1...d5 aims to contest White's control over the center of the board. By occupying the d5 square, Black also prepares to develop the queen's bishop and knight. This move also aims to gain space for Black's pieces, which can lead to a better pawn structure. Playing d5 can also result in the creation of a pawn chain, which can provide some defensive benefits. By responding to White's opening move with d5, Black aims to equalize the position and start building their own position.

The move 2.c4 is a pawn break move by White which helps gain more space in the center. It also attacks Black's d5 pawn and indirectly supports White's pawn on d4. This move also helps White develop the queen's knight to c3 and the queen's bishop to f4 or g5, which can put pressure on Black's position. By playing c4, White aims to control more central squares, and potentially open up lines for their pieces to coordinate and attack Black's position.

In the Queen's Gambit Declined: Modern Variation, Knight Defense, the move 2...e6 is played by Black to protect the d5 pawn and keep control over the central squares. This move also prepares to develop the king's bishop to e7 or d6, which can support Black's pawn structure. By playing e6, Black aims to create a solid pawn chain and avoid any immediate tactics that White may have. This move can also help to restrict the potential of White's pawns on c4 and d4 by limiting the range of the queen's bishop and the queen's knight.

The move 3.Nc3 by White is a common response in many openings as it aims to develop the knight to a more active square. This move also supports the pawn on d4 and puts more pressure on Black's central pawn on d5. By developing the knight to c3, White also prepares to castle kingside and potentially create a battery with the queen behind the pawn on d4. This move can also restrict Black's development options for the light-squared bishop, which may be blocked in by the e6 pawn. Finally, by playing Nc3, White prepares for possible tactical motifs involving a discovered check or fork with the knight.

The move 3...Nf6 by Black aims to develop the knight to an active square and contest White's control over the central squares. This move also prepares to develop the light-squared bishop, typically to b4 or d6. By developing the knight to f6, Black can also put pressure on White's pawn on d4. This move can be part of a plan to exert control over the center and prepare for a counterattack on White's pieces. Moreover, Nf6 allows Black to potentially castle kingside in the future and get the king to a safer position. Finally, this move can also prevent White from playing e5 and gaining more space in the center.

In the Queen's Gambit Declined: Modern Variation, Knight Defense, the move 4.Bg5 by White targets Black's knight on f6. This move also develops the bishop to an active square and prepares to castle kingside. By pinning the knight on f6, White puts pressure on Black's position and potentially gains control over the e7 square. This move also inhibits Black's development of the pawn on f6 or the light-squared bishop. Additionally, Bg5 can also be part of a plan to trade off Black's knight on f6 and potentially weaken Black's pawn structure. Finally, by placing the bishop on g5, White prepares to potentially double their rooks on the d-file if Black decides to capture the pawn on c4.

The move 4...Nbd7 by Black aims to remove the knight from the pin on f6 and prepare to develop the queen's knight to c5 or e7. This move also supports the pawn on d5 and potentially prepares to castle kingside. By playing Nbd7, Black also prevents any potential tactics involving a discovered attack on the queen or the king. Additionally, this move can create a threat of potential counterplay by attacking the bishop on g5 with the queen's knight from c5. By moving the knight to d7, Black also frees up the square f5 for the light-squared bishop, which can be an option in some variations. Finally, this move can be part of a plan to control the center and prepare for a possible pawn break with e5 in the future.

The move 5.e3 by White is played to support the pawn on d4 and prepare to castling kingside. This move also potentially provides protection to the bishop on g5 and may threaten to play dxc5 if Black does not react to it. By playing e3, White also prepares to develop the queen's bishop to e2 or d3, which can reinforce the control over the central squares. Additionally, this move can be part of a plan to control the center and restrict the movements of Black's pieces by creating a pawn chain. Finally, e3 can also prepare for a future pawn break with f4, depending on how Black develops their pieces.

In the Queen's Gambit Declined: Modern Variation, Knight Defense, the move 5...c6 by Black aims to fortify the d5 pawn and prevent any potential tactical ideas involving a discovered attack on the queen or the king. This move can also prepare for the development of the queen's bishop to b4 or d6, which can put pressure on White's pawn structure. By playing c6, Black also prepares for a potential pawn break with dxc4 followed by b5, which can open up lines for the queen and bishop. This move can also limit the movement of White's queen's knight and potentially undermine the pawn on d4. Finally, this move can prepare for a potential exchange on d4, followed by the development of the light-squared bishop to b7.