It is not easy for Black to retain tide Pawn which he has won. If he plays (13) …, B-e7; (14) Kt-f3, Pxe3; White can continue (15) Pxd5 with good attacking chances on account of the open files in the center of the board, of which Black cannot yet make any use as he has not yet castled.
By P-a6 Black opens again the fifth rank in order to operate against the Knight g5.
(14) Ktxd4 Pxc4 (15) Qxc4 B-d7 (16) Kt-b3
A very bad move, as it violates the general principles of strategy. In withdrawing the Knight from the dominating center square White decreases his mobility instead of increasing it. The logical continuation would have been Rf1-d1 or Ra1-c1, developing one of the Rooks.
(16) … Qxg5 (17) Qxb4 B-c6
Black would not have been able to occupy this favorable square with his Bishop, had not White withdrawn his Knight from d4.
(18) P-e4 P-a5
This forces the Queen out of the diagonal a3-f8 as the Pawn e4 has to be kept protected.
(19) Q-d2 Qxd2
Black demonstrates in a very simple manner that the exchange of Queens is disadvantageous for White, a fact that White should have foreseen as the unprotected Knight on d2 enables Black to gain control of the d-file by castling on the Queen's side.