would be no protection as Black could exchange on c3 and then
take the Pawn. Therefore, White must defend the Pawn with another
piece. The Bishop f1, which has to be developed in any case,
offers himself naturally for this purpose, but B-d3 is not
possible as long as the Knight d4 has to be kept protected by the
Queen. Hence, it is necessary first to exchange the Knight.

(6) Ktxc6 Pb7xc6
(7) B-d3 P-d5!

Again Black has succeeded in advancing his Queen's Pawn against
the opposing center-Pawn, and White cannot avoid the exchange. To
advance to e5 would be against the principle that no Pawn-move
should be made in the opening which is not absolutely necessary.
How easily (8) P-e5 could get White into trouble can be seen from
the following variation: (8) ..., Kt-g4; (9) o-o, o-o; (10) Pf4
??, B-c5+; (11) K-h1, Q-h4; (12) P-h3, Q-g3; (13) Pxg4, Q-h4
mate.

III. (3) P-c3

With this move White invites Black to lose time in winning a Pawn
or two while the White pieces are rapidly developed. If Black
accepts the Gambit [Footnote: A Gambit is an opening in which the
sacrifice of a Pawn is offered for the sake of a speedy
development of the pieces.] the continuation might be.

(3) ... Pxc3
(4) B-c4 Pxb2
(5) Bxb2