A difficult but necessary move. White defends against the …b5-b4 advance and prepares to break with f2-f4.
1. e2e4  1... d7d6  2. d2d4  2... g8f6  3. b1c3  3... e7e5  4. g1f3  4... b8d7  5. g2g4 Shirov is fond of playing the g4-move in the opening. White can consider this idea without sacrificing the pawn, playing 5.Rg1 first. 5... f6g4 Accepting the gift. 6. h1g1  6... g4f6  7. f1c4 The g-file is opened and Black has to lose time before finishing the development. The position looks good for White, but it's actually not easy to break Black's defense. 7... h7h6  8. d4e5  8... d6e5  9. c1e3  9... c7c6  10. d1d3  10... b7b5  11. c4b3  11... d8a5  12. e1c1  12... c8a6 