The Closed, Main Line is a variation of the Catalan Opening, catalogued as ECO E09. The line runs 1. d4 Nf6 2. c4 e6 3. Nf3 d5 4. g3 Be7 5. Bg2 O-O 6. O-O c6 7. Qc2 b6 8. Nbd2 Bb7 9. e4 Nbd7, reaching the position shown below after 18 half-moves.
Both sides have pawns in the centre (White on d4 and e4, Black on d5), and two pawn captures are available, so the structure is still fluid. Development is level at three minor pieces each. It is White to move after nine moves. Both kings have castled kingside, so play tends to shift to the centre and the opposite flank.
On the Catalan Opening generally: A sophisticated system combining Queen's Gambit ideas with a fianchettoed king's bishop.
You can play through this variation move by move in your browser — Learn mode walks the line with an explanation at each step, and Drill mode replays it from memory so you find out whether you actually know it. No account is required.
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The Closed, Main Line goes 1. d4 Nf6 2. c4 e6 3. Nf3 d5 4. g3 Be7 5. Bg2 O-O 6. O-O c6 7. Qc2 b6 8. Nbd2 Bb7 9. e4 Nbd7. It is a variation of the Catalan Opening and is catalogued as ECO E09.
The Closed, Main Line is ECO E09. ECO codes group openings by their move order, so nearby codes cover closely related lines of the Catalan Opening.
Stockfish evaluates the position after 1. d4 Nf6 2. c4 e6 3. Nf3 d5 4. g3 Be7 5. Bg2 O-O 6. O-O c6 7. Qc2 b6 8. Nbd2 Bb7 9. e4 Nbd7 at +0.47 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 d4 and e4, Black on d5), and two pawn captures are available, so the structure is still fluid. Development is level at three minor pieces each. It is White to move. Both kings have castled kingside, so play tends to shift to the centre and the opposite flank.