The Quiet Line, 4.O-O Nf6 is a variation of the Hungarian Defense, catalogued as ECO C50. The line runs 1. e4 e5 2. Nf3 Nc6 3. Bc4 Be7 4. O-O Nf6 5. d3 O-O 6. Re1, reaching the position shown below after 11 half-moves.
Both sides have pawns in the centre (White on e4, Black on e5). Development is level at two minor pieces each. It is Black to move after six moves. Both kings have castled kingside, so play tends to shift to the centre and the opposite flank.
On the Hungarian Defense generally: A solid but passive response to the Italian Game. Black develops the bishop to e7 instead of the more active c5, aiming for a quiet positional game.
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The Quiet Line, 4.O-O Nf6 goes 1. e4 e5 2. Nf3 Nc6 3. Bc4 Be7 4. O-O Nf6 5. d3 O-O 6. Re1. It is a variation of the Hungarian Defense and is catalogued as ECO C50.
The Quiet Line, 4.O-O Nf6 is ECO C50. ECO codes group openings by their move order, so nearby codes cover closely related lines of the Hungarian Defense.
Stockfish evaluates the position after 1. e4 e5 2. Nf3 Nc6 3. Bc4 Be7 4. O-O Nf6 5. d3 O-O 6. Re1 at +0.29 at depth 18, which is a slight pull for White, within normal opening margins. Engine evaluation is only a starting point — at club level the practical value of a line is mostly about whether you know its plans better than your opponent does.
Both sides have pawns in the centre (White on e4, Black on e5). Development is level at two minor pieces each. It is Black to move. Both kings have castled kingside, so play tends to shift to the centre and the opposite flank.