(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.

          (20) Ktxd2 o-o-o
          (21) Kt-c4

White cannot play R-d1 on account of R-d4, threatening Rh8-d8.

          (21) ...  Bxe4
          (22) Rf1-c1

This merely drives the Black King to a safe place.  Ktxa5 was indicated.  R-d2 could then have been answered by (23) R-c1+ and (24) R-C4.

          (22) ...  K-b8
          (23) P-f3

Again a move which helps the opponent as it drives the Bishop where he wants to go.

          (23)...  B-d5
          (24) Ktxa5 R-c8
          (25) P-b3

This situation furnishes an instructive example of the importance of the rules governing Pawn formations as previously discussed.  By attacking the Knight with the King Black can force the exchange of the Bishop for the Knight on c4.

+---------------------------------------+
8 |    | #K | #R |    |    |    |    | #R |
|---------------------------------------|
7 |    | #P |    |    |    | #P | #P | #P |
|---------------------------------------|
6 |    |    |    |    | #P |    |    |    |
|---------------------------------------|
5 | ^Kt|    |    | #B |    |    |    |    |
|---------------------------------------|
4 |    |    |    |    |    |    |    |    |
|---------------------------------------|
3 |    | ^P |    |    |    | ^P |    |    |
|---------------------------------------|
2 | ^P |    |    |    |    |    | ^P | ^P |
|---------------------------------------|
1 | ^R |    | ^R |    |    |    | ^K |    |
+---------------------------------------+
a    b    c    d    e    f    g    h

Diagram 73.

This leaves White with a Pawn on c4 who is weak on account of his advanced position.  Black can attack him with the King and White’s King is consequently compelled to stay on the Queen’s wing guarding the Pawn, while Black is at leisure to secure a passed Pawn on the King’s wing.  These maneuvers are, of course, possible only with the Rooks off the board.  That is why Black tries to force their exchange and why White should endeavor to prevent it.

          (25) ...  Rxc1+
          (26) Rxc1 R-c8
          (27) Rxc8+

In view of the hopeless Pawn ending it would have been best to give up a Pawn by (27) R-d1, P-b6; (28) Kt-c4, Bxc4; (29) Pxc4, Rxc4; (30) R-d2 in order to keep a Rook on the board, thus obtaining a drawing chance.