Chess Opening Theory/1. d4/1...Nf6/2. c4/2...g6/3. Nc3/3...d5/4. cxd5/4...Nxd5/5. e4/5...Nxc3/6. bxc3/6...Bg7/7. Nf3/7...c5

7...c5
This move is the key pawn lever, taking advantage of the diagonal. Note that the long diagonal is weak. Without this lever, d4 would be indestructible and the Grunfeld defense would be unsound. White has played four moves, the most theoretical being 8.Rb1.