The Colle System, also known as the Colle–Koltanowski system, is a chess opening strategy for White introduced by Belgian Edgard Colle in the 1920s, and further developed by George Koltanowski. This variation of the Queen's Pawn Game is characterised by a systematic if modest development of White's minor pieces to support a quick pawn move to the e4 square. It is solid, but inflexible.
Colle and Koltanowski each won many tournaments in the 1920s and 1930s. Colle finished ahead of Tartakower, Euwe and Rubinstein at various times. The opening had even been referred to as the “dreaded” Colle System. George Koltanowski, in his book, “The Colle System” said it offered “solid development”, combinations, a decent endgame, and it gives White “good chances of not losing against a stronger player”. However, players like Capablanca and Tal found ways to take the sting out of some of its various lines. One such line that has been tested is 3...Bf5, sometimes called the “Anti-Colle.” 
Ignoring Black's responses in order to consider White's moves only, the typical plan is as follows: 1.d4 2.Nf3 3.e3 4.Bd3 5.0-0 6.Re1 7.c3 8.Nbd2 9.e4, with White rearranging their move order appropriately. It is a perfectly solid scheme of development, but, inflexibly applied, it cannot offer more than equality against a vigorous Black response. It may be a good tool for avoiding book variations, for Blitz play, or for forcing opponents to think for themselves early on. These days it is considered totally innocuous, and is rarely seen at Master level or above.
|This article uses algebraic notation to describe chess moves.|
One variation on the Colle is the Colle–Zukertort System (named for Johannes Zukertort), characterized by developing the dark-squared bishop on b2. The typical plan is: 1.d4 d5 2.Nf3 e6 3.e3 Nf6 4.Bd3 c5 5.b3 Nc6 6.0-0 Bd6 7.Bb2 0-0. In this variation White will eventually play for a kingside attack, despite their apparently innocuous development. This system has been frequently employed at grandmaster level by Artur Yusupov.
The strategic plan behind the Colle System is to aim for a kingside attack. The black king's knight will be either exchanged off on e4, or driven away by the advance e4–e5. This removes a guard from the h7 square, often enabling a classic bishop sacrifice on h7 as the start of a mating attack. Some authors even call this sacrifice "Colle's sacrifice".
- 1.d4 d5 2.Nf3 Nf6 3.e3 c5 4.c3 e6 5.Bd3 Bd6 6.Nbd2 Nbd7 7.0-0 0-0 8.Re1 Re8 9.e4 dxe4 10.Nxe4 Nxe4 11.Bxe4 cxd4 12.Bxh7+ Kxh7 13.Ng5+ Kg6 14.h4 Rh8 15.Rxe6+ Nf6 16.h5+ Kh6 17.Rxd6 Qa5 18.Nxf7+ Kh7 19.Ng5+ Kg8 20.Qb3+ 1–0 (Black resigns)
Black has a variety of approaches to counter the Colle System. One of the most dynamic is to aim for a Queen's Indian Defense style setup. White's pawn push to e4 slashes at empty space, while Black's pieces are poised to undermine White's centre and attack the queenside. The technique is well illustrated in the 1929 game between Colle and José Capablanca:
- 1.d4 Nf6 2.Nf3 b6 3.e3 Bb7 4.Nbd2 e6 5.Bd3 c5 6.0-0 Nc6 7.c3 Be7 8.e4 cxd4 9.Nxd4 0-0 10.Qe2 Ne5 11.Bc2 Qc8 12.f4 Ba6 13.Qd1 Nc6 14.Rf3 g6 15.N2b3 Nxd4 16.Nxd4 Bb7 17.Qe2 Bc5 18.Rh3 Qc6 19.e5 Nd5 20.Qf2 Bxd4 21.cxd4 Rac8 22.Bd1 f6 23.Qh4 Rf7 24.Bf3 Qc4 25.Be3 Nxe3 26.Bxb7 Nf5 27.Qe1 Rc7 28.Be4 Qxd4+ 29.Kh1 fxe5 30.Bxf5 exf5 31.fxe5 Re7 32.Re3 Qxb2 33.e6 dxe6 34.Rxe6 Kf7 0–1 (White resigns)
- Rudel, David. “Koltanowski-Phoenix Attack”. Thinker Press. 2011. p. 84 ISBN 188871056X
- Reinfeld, Fred. “The immortal Games of Capablanca”. Dover. 1970 p. 185 ISBN 0486263339
- Koltanowski, George. “Colle System”. 1980. Chess Enterprises, Inc. ISBN 0-931462-05-3
- John Nunn, Graham Burgess, John Emms, and Joe Gallagher. Nunn's Chess Openings. Everyman Publishers, London, 1999.
- Colle vs. O'Hanlon
- Colle vs. Capablanca
- Palliser, Richard (2008). Starting out: d-pawn attacks – The Colle-Zukertort, Barry and 150 Attacks. Everyman Chess. ISBN 978-1-85744-578-7.
- Rudel, David (2009). Bxh7+. Thinkers Press. ISBN 1-888710-37-3.
- Rudel, David (2009). Zuke 'Em: The Colle–Zukertort Revolutionized. Thinkers Press. ISBN 1-888710-39-X.
- Lane, Gary (2001). The Ultimate Colle. Sterling Pub Co Inc. ISBN 978-0-7134-8686-5.
- Broznik, Valeri (2003). The Colle-Koltanowski System. Kania. ISBN 3-931192-25-3.
- Palliser, Richard (2007). Starting out: the Colle. Everyman Chess. ISBN 978-1-85744-527-5.