Black is not obliged to allow this transposition though: 7...Bg7 is also playable. After 8.e4 0-0 9.Be2, Black has alternatives to 9...Re8, such as the 9...Na6 10.0-0 Ne8 Kramnik played against Leko at the 2004 World Championship, where Black intends to attack White's centre with ...f5. Alternatively, if White immediately completes the knight manoeuvre and attacks the pawn on d6 with 8.Nc4 0-0 9.Bf4, Black can either defend it with 9...Ne8 or sacrifice it with 9...Na6 or 9...b6.