With this move Black crosses White's plans by exchanging the Bishop who was to play the main part in the attack, and, as a consequence, the Knight g5 does not have a chance to do any useful work either.
(9) P-d6
Opening again the diagonal of the Bishop and getting rid of the advanced Pawn by exchange before Black has an occasion to capture him.
(9) … Ktxb3 (10) Pxc7 Qxc7
+———————————————————-+
8 | #R | | #B | | #K | #B | | #R |
|———————————————————-|
7 | | | #Q | | | #P | #P | #P |
|———————————————————-|
6 | #P | | | | | #Kt| | |
|———————————————————-|
5 | | #P | | | #P | | ^Kt| |
|———————————————————-|
4 | | | | | | | | |
|———————————————————-|
3 | | #Kt| | ^P | | | | |
|———————————————————-|
2 | ^P | ^P | ^P | | | ^P | ^P | ^P |
|———————————————————-|
1 | ^R | ^Kt| ^B | ^Q | ^K | | | ^R |
+———————————————————-+
a b c d e f g h
DIAGRAM 65.
Black could regain his Pawn by Q-d5; (11) Pa2xb3, Qxg2; (12) Q- f3, Qxf3; (13) Ktxf3, B-b7; (14) K-e2, B-d6 and Bxc7; but in doing so he would give up his advantage in development, which, as the further course of the game proves, is much more valuable.
(11) Pa2xb3 B-b7 (12) o-o P-h6!
If Black proceeded to develop his pieces indiscriminately, his advantage would soon vanish. White needs only two moves—R-e1 and Kt-e4—to paralyze the effect of Black's powerful Queen's Bishop and to regain control of the center where at present Black has the upper hand on account of his center-Pawn.
(13) Kt-f3 B-d6 (14) R-e1 o-o (15) Ktb1-d2 Ra8-d8 (16) P-c3