Thus weak points are created of which White may find an
opportunity to make use in a manner similar to the one
illustrated by the discussion of Diagrams 26 and 29. On the other
hand, Black gains an open file for his Rooks as soon as the g-
Pawn is out of the way, and the exchange on f6 should therefore
not be made until preparations for the occupation of the
resulting weak spots are completed. The following variations will
throw some light on this rather complex problem.

Supposing White wants to try the immediate exchange on f6, hoping
that somehow or other he will be able to take advantage of the
weakness resulting on f6 and h6. In exchanging he can give up
either his Knight d5 or his Bishop g5. In both cases there are
promising possibilities for attack, but Black, with correct play,
can sufficiently defend himself and even get the better.

If White plays (1) Ktxf6 he has to lose a move before he can
bring up other pieces to help in the attack, for after Pxf6 he
must first move the Bishop g5. The only good square for the
Bishop is h4 from where he maintains the pin on f6 which would
become very dangerous for Black if he could not prevent White's
Queen from entering on h6 or render the double threat on f6
ineffective in some other way. The logical continuation for Black
is to answer (2) B-h4 with K-h8 in order to occupy the g-file
with his Rook as soon as possible. Indeed, this is at the same
time the best defense against White's threat, for if White now
plays (3) Q-d2; Black replies Ktxf3+; (4) Pxf3, Bxf3; and he is
the first to take advantage of the open g-file as his King has
already made room for the Rook.