The Tiviakov game shows how to react to the wing attack ...g5: a counterblow in the center d4 even if this costs a tempo. ...g5 has made ...O-O near impossible and at e8 the king is unsafe if lines open.
...g5 is only justified after h3.
@tpr #11
Well, what a move h3, if Black has not yet made a move 0-0. Question: Is move 6. c3 a mistake?
Yes, 6 c3 looks like a mistake. Tiviakov's 6 d4 is much more active as it prepares Nxe5 in response to ...g4.
7 Nh4 is definitely a mistake, as it loses a pawn. White has to settle for 7 Ne1, but that is a sign white has done something wrong.
White missed Bxf7+ interesting