Modern Defense: Semi-Averbakh Variation, Pterodactyl Variation Declined

One of the most popular and fundamental chess openings is the one that starts with the move 1.e4. This move signals an intention to control the central squares of the board, and is a way for white to begin an active and aggressive game. With 1.e4, white also opens lines of play for the development of the pieces, creating the potential for fast and powerful attacks against black's position.

Upon seeing white's 1.e4, black decides to respond with the move g6, which is a flexible and solid choice. Black aims to control the important diagonal that runs from a8 to h1, which is often used by white's dark-squared bishop. This move also prepares to fianchetto Black's own dark-squared bishop, strengthening Black's kingside and creating opportunities for counterplay. By delaying pawn moves in the center, Black chooses to develop pieces harmoniously, rather than engaging in an early battle for control of the center.

White's move 2. d4 is a logical continuation of the opening plan because it aims to seize control of the central squares, break Black's pawn chain, and create more space for White's pieces to maneuver. By advancing the d-pawn, White puts pressure on Black's knight on f6, which could be forced to move and further disrupt Black's development. Additionally, this move can also open lines for the development of White's queen and bishop, preparing for possible future attacks against Black's weakened pawn structure.

In the Modern Defense: Semi-Averbakh Variation, Pterodactyl Variation Declined, Black's move 2...Bg7 is a natural and important move, developing the bishop to its most active square and preparing to castle kingside. Placing the bishop on g7 also allows for a solid pawn structure with pawns on g6 and d6, that can support each other and resist white's potential pawn breaks. Furthermore, by developing a piece on the kingside, Black strengthens the defense of their king, which is important as white's space advantage could lead to potential tactical opportunities. Finally, the bishop on g7 also has the potential to become a powerful attacking piece in combination with other pieces.

White's move 3. c4 is a central pawn break that aims to gain control of the d5 square, preventing Black's d6 pawn to advance and blockading it. By advancing the c-pawn, White gains space on the queenside, preparing to develop the knight to c3 and potentially supporting a future attack towards Black's king. The move c4 can also allow White to free up the bishop on c1, giving it more freedom to move and control important squares. Finally, sometimes the move c4 is played to avoid facing the Grunfeld Defense when Black plays d5.

Black's move 3...c5 breaks open the center and fights for control of the d4 square. By advancing the c-pawn, Black gains space in the center and attacks White's pawn on d4, which can no longer be defended by the knight on f3. This pawn break can also help to relieve the pressure on Black's position and can limit White's potential for pawn advances on the queenside. Furthermore, by playing c5, Black prepares to develop the knight on c6 and the queen on c7, making a strong formation with a wide range of tactical and strategic options to choose from.

In the Modern Defense: Semi-Averbakh Variation, Pterodactyl Variation Declined, White's move 4.Nf3 develops the knight and prepares to recapture the pawn on d4. Additionally, the knight on f3 supports the control of central squares, especially e5, which may be an option for White to advance the e-pawn in the future. Developing the knight to f3 also prepares to castle kingside, providing additional protection to White's king, which could be under pressure from Black's pawn pushes on the queenside. Finally, the move Nf3 also prepares white to continue developing their pieces with moves such as Be3 and 0-0.

Black's move 4...d6 solidifies the pawn structure and develops the bishop on g7 that was previously blocked by the pawn on d6. This move can also block White's pressure on Black's pawn on c5, even though the black queen no longer has control over the square b6. Additionally, Black's pawn on d6 can support the knight on f6, which improves defense and central control. Finally, moving the d-pawn also prepares for castling kingside, protecting the king and giving the rook access to the center files.

White's move 5.Be2 develops the bishop to a natural square and prepares to castle kingside, providing additional protection to their king while connecting the rooks. Additionally, by placing the bishop on e2, White improves their control over the diagonal a8-h1, which previously was blocked by Black's pawn on c5. This move also frees the d1-square for the queen, which can be useful in creating an attack on the kingside or participating in a pawn break in the center. Finally, the bishop on e2 can act as a defender of the kingside and support future attacks on the queenside.

In the Modern Defense: Semi-Averbakh Variation, Pterodactyl Variation Declined, Black's move 5...Qa5+ aims to disrupt White's development and gain tempo while attacking the bishop on e2. By checking the king, Black stops White from playing the natural castle kingside move and forces White to move their king or defend with the knight. Additionally, this move can potentially lead to a forced exchange of bishops after Bd2, which can benefit Black's position by weakening White's pawn structure. Finally, the queen on a5 can eye the square c5, from which Black can launch a potential attack on White's central pawns.