Preparing the exchange of the main defender of the e4-square, the knight on c3.
From here the knight can join the battle for the e4-square via d6 or even g3.
4.a3 Bxc3 5.Bxc3 g6 6.Bb4 Ne4 7.Qf4 Nfg3! 8.Qe5 Qd7 9.Rxc8 Rxc8 10.Bxe4 Nxe4 11.Rf1 Qe6! 12.Qxe6 fxe6
White methodically improves his position, waiting with Nf3-e5 until the f4-pawn is safe, and a pin with Bh5 no longer exists.
With the centre dominated by his strong knight, White launches a kingside attack.