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

Diag. 123

20. ...  B-KB3 21.  P-Kt4 P-Kt 22.  P-B5 P-Q6 23.  BxP BxKP

If PxKP then 24.  PxKtP, Kt-K4; 25.  RxKt, BxR; 26.  Q-R5, Q-B3; 27.  RxQ, BxR; 28.  PxPch, K-R1; 29.  Q-B7, etc.; or 26. ...  BxP; 27.  B-B8, etc.

24.  PxB                Q-Kt3ch
25.  K-R1               Resigns

Game No. 17

White:  Berlin.  Black:  Riga.

Ruy Lopez.

Move 1-6 as in Game No. 16.

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

Diag. 124

6. ...  PxP

Compare note to move No. 6 in Game 14.

7.  R-K1              P-Q4
8.  KtxP              B-Q3

This is the key to the variation.  Black threatens to obtain a draw by perpetual check through BxPch, followed by Q-R5ch and QxPch.  This is not good enough against a weaker opponent in a tournament, and a strong player cannot afford to play the Riga defence.  But that is not a point against the variation.  To prove it unsound, White has to find a win.

9.  KtxKt BxPch
10.  K-R1!

After 10.  K-B1 Black has a tremendous attack, and drives it home before White can manage to bring his extra piece into play.  A game Maroczy-Berger (Vienna, 1908) is an illustration of this.  It continued in this way:  10.  K-B1, Q-R5; 11.  B-K3, Castles; 12.  Kt-Q4, B-Kt5; 13.  Kt-KB3, Q-R4.  Now White has no satisfactory continuation. 14.  Kt-Q2 obstructs the Queen, and it is difficult to bring the Rooks into concerted action. 14.  Kt-B3, QR-Q1; 15.  Q-Q3, BxKt; 16.  PxB, QxP; 17.  KtxKt, PxKt; 18.  Q-B3, Q-R6ch; 19.  K-K2, Q-Kt5ch; 20.  K-B1, R-Q4; 21.  B-Kt3, R-KR4; 22.  P-B3, PxP; Resigns.