Réti Opening: Anglo-Slav Variation, London Defensive System

In the Réti Opening: Anglo-Slav Variation, London Defensive System, White starts with 1. c4. This move is aimed at controlling the center of the board and preparing for a strong pawn advance. By playing c4, White intends to open up lines for the queen and bishop, while challenging Black's control over the d5 square. Moreover, c4 is a flexible move, as it allows White to transpose into a variety of different openings depending on Black's response. In sum, 1. c4 is a key move in the Réti Opening, offering a versatile starting position for White with plenty of potential for aggressive play.

Black's 1... Nf6 move is a standard response to 1. c4, aiming to contest control over the center squares of the board. This move supports Black's own pawn advance to e5, and also prepares to attack White's pawn on c4. Moreover, the knight on f6 can potentially control the d5 square, which is a critical square in many pawn structures. By playing 1... Nf6, Black is looking to establish a solid position with a flexible pawn structure that allows for both defensive and offensive options.

White's move 2. g3 is a flexible setup that aims to control the long diagonal and prepare castling. By playing g3, White intends to fianchetto the bishop on g2, putting pressure on the center and potentially preparing for a kingside attack. Moreover, this pawn move helps to reinforce the pawn structure, protecting the c4 pawn and preventing a Black pawn push to d5. The move g3 also allows White to avoid certain lines of the Sicilian Defense, while maintaining strong control over the board. In sum, g3 is a solid and versatile move that offers many strategic options for White in the opening.

In the Réti Opening: Anglo-Slav Variation, London Defensive System, Black's move 2... c6 is a standard response to g3 that prepares to establish a solid pawn on d5. By playing this move, Black prevents White from playing d4 and establishing a strong pawn center. Additionally, the pawn on c6 supports a possible b7-b5 pawn break, which can put pressure on White's pawn structure and potentially open up lines for Black's pieces. Furthermore, c6 also protects the knight on d5, which is a key defender of Black's position. In sum, 2... c6 is a flexible and strategic move that acts as a strong defense, while also creating opportunities for counterplay.

White's move 3. Nf3 is a natural developing move that brings the knight closer to the center of the board while preparing for castling. By playing Nf3, White also puts pressure on Black's pawn on d5, potentially forcing it to move or creating an opportunity to capture with the knight. Nf3 also supports a possible pawn push to e4, which can help to open up lines for White's pieces and gain more space on the board. Moreover, this knight can potentially help to control key central squares, such as e5 and d4. In sum, Nf3 is a versatile and flexible move that sets up White's position for future strategic play.

Black's 3... d5 move is a typical central pawn break that aims to control the center of the board and challenge White's pawn on c4. By playing d5, Black also frees up space for the development of the queen's bishop and possibly the knight on c6. Moreover, this move can potentially lead to a pawn trade and open up lines for Black's pieces. Additionally, the pawn on d5 helps to control the square c4, limiting the scope of White's knight and preventing any potential invasion by the queen. In sum, d5 is a strong and aggressive move that offers many tactical possibilities for Black in the opening.

In the Réti Opening: Anglo-Slav Variation, London Defensive System, White's move 4. b3 is a relatively quiet move that aims to control the diagonal b1-h7 with the bishop while setting up a potential fianchetto. The b3 pawn also provides support for the bishop should it need to retreat to b2. Moreover, this move prevents any potential queen invasion on the a4-e8 diagonal while supporting a future pawn push to c5, which can help to undermine Black's pawn structure. Additionally, b3 sets the stage for a flexible pawn structure that allows for various pawn breaks and strategic options depending on Black's response. In sum, b3 is a solid and strategic move that helps to solidify White's position on the board.

Black's move 4... Bf5 is a solid developing move that seeks to challenge White's control over the e4 square and potentially trade off one of White's key bishops. By playing Bf5, Black also prepares to castle kingside and brings the bishop to an active position where it can influence the center and defend against potential attacking ideas. Moreover, this move can potentially put pressure on White's pawn structure by attacking the pawn on b3. Additionally, the bishop on f5 controls the long diagonal, making it difficult for White to set up a strong fianchetto. In sum, 4... Bf5 is a flexible move that helps to establish Black's position while creating potential for future tactical opportunities.