5. ...  P-Q3

Here Black might have played P-Q4 at once.  For if White takes the pawn, he leaves Black in possession of the pawn in the centre.  If he does not do so but plays B-QKt5 instead, Black’s reply would be Q-K2 and the exchange of pawns at K 5 would follow.  White’s P-B3 is then clearly a lost move.

6.  B-K3 B-Kt3 7.  QKt-Q2 Kt-K2 8.  Kt-B1 P-B3 9.  Q-K2 Castles 10.  Kt-Kt3 P-Q4 11.  PxP PxP 12.  B-Kt3 Kt-Kt3

Black has now the superior position on account of his pawn centre.

13.  Castles KR    B-B2
14.  B-Kt5         P-KR3
15.  BxKt          PxB

There is nothing in the weakness at Black’s KB3 and KR3 caused by the disappearance of his KKt Pawn, as White has lost his KB.  On the contrary the open file should be a distinct asset, for, having a strong centre, Black’s pieces are more mobile and he is more likely to get an attack.

          16.  Q-K3 K-R2
          17.  P-KR3

in order to play Kt-R5, which otherwise would be answered by B-Kt5.

17. ...            KR-Kt1
18.  K-R1          P-B4
19.  Kt-R5         B-K3

BxP was threatened.

          20.  R-KKt1 P-B5

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

Diag. 105

P-K5 would seem to be better, as it opens a diagonal for the KB, and a diagonal, too, for the QB, as White has to exchange the pawns.  Indeed Black would soon have obtained a winning advantage, e.g. 20. ...  P-K5; 21.  PxP (Kt-R2, Q-R5; 22.  Q-K2, Kt-K4), BPxP; 22.  Kt-R2, Q-R5; 23.  Q-K2 (P-KKt4 or B-Q1, P-B4), Kt-K4, threatening Kt-Kt5 and Kt-Q6.  As it is, White gains a little time, although Black’s position still remains superior.

21.  Q-K2          Q-K2
22.  P-Kt4         P-B3

to prevent P-Kt5.

          23.  R-Kt2 QR-K1
          24.  R-K1 Q-B2
          25.  Kt-Q2

intending to play P-B3, thus retarding Black’s P-K5, which is still hanging over White like Damocles’ sword.  The move, however, lets in the Knight.

25. ...            Kt-R5
26.  R-R2          P-B4
27.  P-B3          P-K5

Now this move is no longer feasible, as White’s brilliant sacrifice demonstrates.  To make the move possible, long preparations would have been necessary, such as:  R-Kt3, B-Q2-B3, etc.