To prevent Black from playing 27.... R to Q 7, which would be a powerful
move, as it would attack White's pawns on the Queen's side.
... 27. Q to B 5 (?)
28. Kt (R 4) to B 5 ...
Black.
+---------------------------------------+
| | | | #R | | | | |
|---------------------------------------|
| | #P | #P | | | #P | | #K |
|---------------------------------------|
| | #P | #Kt| | | #Kt| #P | #P |
|---------------------------------------|
| | | | | #P | ^Kt| | |
|---------------------------------------|
| | | #Q | | ^P | | | |
|---------------------------------------|
| ^P | | ^P | | ^Q | | ^Kt| ^P |
|---------------------------------------|
| | ^P | | | | ^P | ^P | |
|---------------------------------------|
| | | | | | ^R | ^K | |
+---------------------------------------+
White.
FIG. 8.
[POSITION AFTER WHITE'S 28TH MOVE.]
(The position being highly instructive, it is illustrated in Fig. 8. White
sacrifices a piece on the chance of Black not seeing the right defence. In
which case the subtle threat is as follows--
... 28. P takes Kt
29. Kt takes P 29. Kt to Kt sq.
Defending the threatened R P.