#4th themematch BTAT, Grünfeld Defense, 5+ players

The Grünfeld Defence (ECO codes D70–D99) is a chess opening characterised by the moves: 1. d4 Nf6 2. c4 g6 3. Nc3 d5 Black offers White the possibility of 4.cxd5, which may be followed by 4...Nxd5 and 5.e4, giving White an imposing central pawn duo. If White does not take the d5-pawn, Black may eventually play ...dxc4, when a White response of e4 again leads to the same pawn structure. In classical opening theory this imposing pawn centre was held to give White a large advantage, but the hypermodern school, which was coming to the fore in the 1920s, held that a large pawn centre could be a liability rather than an asset. The Grünfeld is therefore a key hypermodern opening, showing in stark terms how a large pawn centre can either be a powerful battering ram or a target for attack.