Colle System

White opts for the Colle System, a system opening where their main idea is to prepare an eventual e4 pawn-break. The system knows two set-ups: the traditional Colle, and the Colle-Zukertort system.

The traditional Colle is characterized by the upcoming moves Bd3, c3 and Nbd2. This is the way the Edgard Colle, whom the opening is named after, played the system.^[1]

The Colle-Zukertort system is slightly different from the traditional Colle. The dark-squared bishop is quite passive in the Colle system, so instead of playing c3, White can play b3, preparing to fianchetto the bishop. The b3-pawn also supports the potential c2-c4 in the future.

Since White's next few moves are fairly predictable, Black can choose their own set-up quite freely.

3...e6 is played most frequently. Black will usually go for their own set-up with ...Bd3, either ...Nc6 or ...Nbd7, ...c5 and ...b6.

3...c5 postpones ...e6 in order to possibly develop the light-squared bishop outside of the pawn-chain (generally to g4, pinning White's knight to the queen).

3...Bf5 is the anti-Colle. White can't continue with their system since Black will simply trade light-squared bishops. Therefore, White's usual response is 4. c4, transposing into the Slav defence. A similar transposition occurs after 3...c6.

1. d4 Nf6 2. Nf3 d5 3. e3

• "The Colle System, Lecture by GM Ben Finegold". www.youtube.com.
• "The Colle System - Plans, Structures, Patterns, Variations · Chess Openings". www.youtube.com.

Wikipedia has related information at Colle System.