Here White could still obtain a freer game with P-Q4.  Perhaps he was afraid of losing a pawn after 6. ...  PxP; 7.  KtxP, KtxP.  But there is nothing in it, e.g. 8.  KKtxKt, KtxKt; 9.  KtxQ, KtxQ; 10.  KtxBP! (KtxKtP?  BxKt; 11.  BxB, R-QKt1), KxKt (KtxBP?; 11.  KtxR, KtxR; 12.  KtxP, KtxP; 13.  KtxP), KxKt.  There was nothing else to be feared after P-Q4.

6. ...               P-Q3
7.  Castles          B-Q2

in order to play Q-B1 and B-R6 and to exchange Bishops, after which there would be weak points at White’s KR3 and KB3.

8.  P-KR3             Castles
9.  B-K3              P-KR3

Black also prevents an exchange of Bishops.

10.  Q-Q2              K-R2
11.  P-B4              Kt-K1

The position has now become exceedingly difficult.  In order to make the most of the favourable development of his KB, Black must advance on the Queen’s side.  But in moving his King’s side pieces over to the Queen’s side, Black must proceed warily, as White might get chances of an attack with overwhelming forces on the King’s side.

12.  P-KKt4 Kt-B2
13.  Kt-Kt3

Here it was necessary to play R-B2 in order to play the QR to KB1 before Black could manage to drive the Kt to Q1 by P-QKt4-5.

13. ...  P-QKt4
14.  Kt-Q1?

It would still have been better to play QR-K1 and to leave the Queen’s side to itself as long as possible after P-Kt5, 15.  Kt-Q1, in order to start an assault on the King’s side with P-B5, P-KR4 and P-Kt5.  After the text move the Queen’s Rook remains shut in.

14. ...  QR-Kt1
15.  Kt-K2

in order to play P-B3 and P-Q4.  The whole plan, however, is inconsequent, as he has started an attack on the King’s side.  Now he suddenly opens up files on the Queen’s side where Black has assembled superior forces.  The result is that White gets into trouble on both wings, for as soon as he gives up his King’s side attack, the advanced pawns there, as one knows, are only a source of weakness.

15. ...  P-Kt5 16.  P-B3 PxP 17.  PxP Q-B1 18.  P-Q4 PxP 19.  PxP Q-R3 20.  R-B1 Kt-Kt4 21.  P-Q5

---------------------------------------
8 |    | #R |    |    |    | #R |    |    |
|---------------------------------------|
7 | #P |    |    | #B | #P | #P | #B | #K |
|---------------------------------------|
6 | #Q |    | #Kt| #P |    |    | #P | #P |
|---------------------------------------|
5 |    | #Kt|    | ^P |    |    |    |    |
|---------------------------------------|
4 |    |    |    |    | ^P | ^P | ^P |    |
|---------------------------------------|
3 |    |    |    |    | ^B |    |    | ^P |
|---------------------------------------|
2 | ^P |    |    | ^Q | ^Kt|    | ^B |    |
|---------------------------------------|
1 |    |    | ^R | ^Kt|    | ^R | ^K |    |
---------------------------------------
A    B    C    D    E    F    G    H

Diag. 143