The Colle System, also known as the Colle-Koltanowski System, is a chess opening for White, popularized in the 1920s by the Belgian master Edgard Colle and further developed by George Koltanowski. The Colle is characterized by several moves. White's center pawns are developed to d4 and e3, the king's knight is developed to f3, the king's bishop is developed to d3, and the queen bishop's pawn (c-pawn) is developed to c3. Common continuations include development of the queen's knight to d2 (Nbd2) and kingside castling (0-0). A major theme of the Colle System is the ambition to play a well-timed e4, where the square is defended by the bishop at d3, the knight at d2 (following Nbd2), and possibly the rook at e1 (following 0-0 and Re1). Although sometimes described as a specific sequence of moves, the Colle System is not a fixed line of play, but rather a system for White where the moves may be permuted at the player's discretion. When a game opens with most or all of the above moves, to the exclusion of moves which typify other openings, the game may be described as "a Colle System". Although criticized by some and used infrequently in master play, the Colle is regarded by others as a and opening. Definition and assessment The Encyclopedia of Chess Openings identifies the Colle System as an uncommon continuation of the Queen's Pawn Game, assigning it the code D05. In the ECO, the Colle system is defined by the line 1. d4 d5 2. Nf3 Nf6 3. e3 e6 4. Bd3 c5 5. c3. Paul van der Sterren gives an identical definition, with the same moves played in the same order. Other authors clarify that the system refers specifically to White's moves. Hooper and Whyld define the Colle as d4, Nf3, e3, Nbd2, c3 and Bd3 (in no particular order), including Nbd2 in their definition rather than noting it as a usual continuation. Benjamin and Schiller give the broader, less specific definition 1. d4, 2. Nf3, 3. e3, although they also note that the immediate plan involves developing the "f1 bishop". John Nunn et al. regard the Colle as totally innocuous. While acknowledging the system's "innocuous" reputation and its "slow and solid" plan of development, Benjamin and Schiller recommended the Colle as a "good" example of an unorthodox opening, as opposed to a "bad" or "ugly" one. Together with Benjamin and