Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...f6/4. O-O/4...Bc5/5. c3

Nürnberg Variation, Main Line
In this line, White castles to protect the king and prepares to play d4 to gain more space in the center. Black develops the bishop to c5, which is a natural square for the bishop and also puts pressure on the f2-pawn. White plays c3 to support the d4-pawn advance.

The Main Line of the Nürnberg Variation is considered to be better for White, as White has more options and flexibility in the position. White can choose to play d4 immediately or delay it and play Re1, h3, or a4 first. White can also exchange the light-squared bishop on b5 with the knight on c6 at any time, creating a weakness in Black’s pawn structure.

Black, on the other hand, has to deal with several problems in the Main Line of the Nürnberg Variation. Black has to find a good square for the knight on g8, which is blocked by the f6-pawn. Black also has to decide whether to castle kingside or queenside, as both sides have their drawbacks. Black’s king is also vulnerable to attacks by White’s pieces, such as Qf3, Qg4 or Qh5.

Therefore, the Main Line of the Nürnberg Variation is not very popular among chess players, as Black has to struggle for equality. Most players prefer to play other variations of the Spanish Game, such as the Berlin Defense, the Marshall Attack, or the Open Variation. These variations do not involve the move f6 and give Black more chances for counterplay.

'''1. e4 e5 2. Nf3 Nc6 3. Bb5 f6 4. O-O Bc5 5. c3'''