A radical way of preventing the advance.
1. e2e4  1... c7c5  2. g1f3  2... d7d6  3. d2d4  3... c5d4  4. f3d4  4... g8f6  5. b1c3  5... a7a6  6. h1g1 This seemingly primitive move, with the unmistakable intention of advancing the pawn to g4, has become a dangerous weapon in the hands of many grandmasters. It makes sense; after all, why worry about not being able to short-castle if White wants to take the king to the other side $2