The Colle System is a variation of the Queen's Pawn Game, catalogued as ECO D05. The line runs 1. d4 d5 2. Nf3 Nf6 3. e3 e6 4. b3 c5 5. Bb2 Nc6, reaching the position shown below after 10 half-moves.
Both sides have pawns in the centre (White on d4, Black on d5), and one pawn capture is available, so the structure has not settled yet. Development is level at two minor pieces each. It is White to move after five moves.
On the Queen's Pawn Game generally: General term for openings beginning with 1.d4. Leads to strategic, positional play.
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The Colle System goes 1. d4 d5 2. Nf3 Nf6 3. e3 e6 4. b3 c5 5. Bb2 Nc6. It is a variation of the Queen's Pawn Game and is catalogued as ECO D05.
The Colle System is ECO D05. ECO codes group openings by their move order, so nearby codes cover closely related lines of the Queen's Pawn Game.
Stockfish evaluates the position after 1. d4 d5 2. Nf3 Nf6 3. e3 e6 4. b3 c5 5. Bb2 Nc6 at +0.07 at depth 18, which is balanced. 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, Black on d5), and one pawn capture is available, so the structure has not settled yet. Development is level at two minor pieces each. It is White to move.