The Colle System is a chess opening strategy for White introduced by Belgian Edgard Colle in the 1920s. Also known as the Colle-Koltanowski system, played frequently and further developed by the late 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.
Ignoring Black's responses for the time being, the typical plan is as follows: 1. d4 2. e3 3. Nf3 4. Bd3 5. 0-0 6. Re1 7. c3 8. Nbd2 9. e4, with White re-arranging his 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.
One variation on the Colle is the Colle-Zukertort System characterized by developing the dark-squared bishop on b2. The typical plan is: 1. d4 2. Nf3 3. e3 4. Bd3 5. b3 6. Bb2 7. Nbd2 8. 0-0 In this variation White will make an attempt to free both bishops while black will attempt to trap one or both. This system has been seen at Grandmaster level.
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".
A famous Colle system win featuring a slightly unusual Bxh7 sacrifice is Colle-O'Hanlon, 1930. Analysts have squabbled over this sacrifice's theoretical soundness for many years.
1.d4 d5 2.Nf3 Nf6 3.e3 c5 4.c3 e6 5.Bd3 Bd6 6.Nbd2 Nbd7 7.O-O O-O 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 style set-up. 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 game Colle-Capablanca, 1929:
1.d4 Nf6 2.Nf3 b6 3.e3 Bb7 4.Nbd2 e6 5.Bd3 c5 6.O-O Nc6 7.c3 Be7 8.e4 cxd4 9.Nxd4 O-O 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)