Old Indian Defense: Janowski Variation, Grinberg Gambit

Chess players who begin with 1. d4 aim to take control of the central squares of the board early on. This move prepares for the advance of the c-pawn, which will help create a strong position in the center of the board, limiting Black's options. By playing 2. c4, White fights to create a pawn majority in the center and opens the possibility of following up with moves such as Nf3 and e3, further developing their pieces.

Black's move Nf6 is a flexible and common response to 1. d4. With this move, Black aims to control the central squares by putting pressure on White's pawn on d4. Additionally, Nf6 prepares for the push of Black's own e-pawn to e5, which could potentially dominate the center of the board. By playing Nf6, Black also develops a piece, preparing for future moves to follow.

White's move c4 is known as the Queen's Pawn Opening, which is a very popular move, second only to 1.e4. This move aims to control the center and bolster the pawn on d4. Additionally, it frees the queen's bishop to move to its optimal square on c2 or b3. By pushing the c-pawn, White also gains space on the board, making it more challenging for Black to find a good counterattack. Finally, c4 prepares White to follow up with a number of aggressive and flexible moves, including Nc3 and/or e4.

In the Old Indian Defense: Janowski Variation, Grinberg Gambit, Black's move d6 is a characteristic response after White plays c4. With this move, Black prepares to develop their light-squared bishop to f5 and complete their pawn structure. Additionally, d6 provides excellent support to the knight on f6 and removes any potential pins from White's light-squared bishop. By playing d6, Black also strengthens their position in the center of the board and maintains flexibility in their approach, which can make it more challenging for White to develop their pieces with ease.

White's move Nc3 is a common developing move, which aims to control the center and reinforce the pawn chain on d4 and e4. Additionally, Nc3 prepares to advance the e-pawn, which can help to create a strong and flexible pawn structure. By playing Nc3, White also develops a piece and prepares for future moves such as Bd3, which can further increase pressure on Black's position. Nc3 also maintains the option to castle kingside or queenside, which can allow White to choose the optimal position for their king based on how the game progresses.

Black's move Bf5 is a key move in many variations of the Indian Defense, which aims to develop the bishop with tempo, attacking the White's knight on c3. This move also prepares to castle kingside and control key central squares on e4 and d5. The bishop on f5 prevents White from playing e4 easily and challenges the pawn on c4. Additionally, Bf5 pins the knight on c3, limiting White's options for developing their pieces. By playing Bf5, Black aims to both develop a piece and create positional pressure on White's position.

In the Old Indian Defense: Janowski Variation, Grinberg Gambit, White's move e4 is an aggressive pawn thrust, which aims to control the key central squares of the board and challenge Black's position. By pushing the pawn to e4, White aims to gain more space, free up their pieces, and open up the position, which could potentially expose weaknesses in Black's position. Additionally, e4 prepares to follow up with f4, which can further increase the pressure on Black's position and limit their options for development. By playing e4, White aims to both seize control of the center of the board and initiate an aggressive attack on Black's position.