Originally posted by agentreno
Playing as white with the Colle system, there's a move by black that doesn't seem to be often played and I'm sure must have a strong refutation but I can't see anything wrong with it. Can anyone see how this is to blacks disadvantage?
1. d4 d5
2. Nf3 Nf6
3. e3 c5
4. Nbd2 Nbd2
5. c3 e6
6. Bd3 c4?!
Black's pawn push creates a strong pawn chain ext ...[text shortened]... move? Or bad move?
[fen]r1bqkb1r/pp1n1ppp/4pn2/3p4/2pP4/2PBPN2/PP1N1PPP/R1BQK2R[/fen]
It looks a bit dubious to me, but I doubt there's an out and out refutation leading to a win for white. The main problem is the move releases central tension, making the e3-e4 break more powerful for white. If after that black plays d5xe4, then white has dominance in the centre, nice diaganols for his bishops, and black will also have to do something about the potentially weak c4 pawn. If black doesn't play d5xe4 after e3-e4, white can consider e4-e5, also claiming more space in the centre and kingside. The position would then resemble a French Defence, in an opening where c5-c4 is generally considered dubious for black. The second problem is that you might be able to undermine the black pawns with b3 and possibly a4 - although this will depend on the timing of c5-c4 from black.
It's not true incidentally that white never plays c4-c5 in the Queen's Gambit or that it's a necessarily big error - although it is true that it is a rare choice, as white's play in the QGD is usually about putting pressure on the black centre. Anyway, white often goes c4-c5 in the Slav, in positions where two conditions are met: 1. white has Bf4 (thus making the freeing ...e5 very hard for black to successfully achieve) and 2. where black has played ...a6, meaning either that there are more queenside holes for white to probe after c4-c5, or that it's harder for black to undermine the cramping pawn (...b6 cxb6 opens the c-file when the c-pawn is weak; without an early... a6 from black, if white goes c5 black can play ...b6 and if cxb6 axb6 with the idea of ...c5.) There are some comparable lines in the normal QGD where white also plays c4-c5 although it's rarer than in the Slav.