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

DIAGRAM 38.

The way in which White would obtain the advantage is this:

(1) R-e1 B-f5
(2) Rxe4 Bxe4
(3) R-e1

Through sacrificing one Rook for the Knight White has freed the
square e1 for the other Rook who now pins the Black Bishop
without Black being able to protect it.

The position of Diagram 39 is somewhat related to that of Diagram
38, as far as the possibility of a sacrifice for the sake of a
pin is concerned. If White plays B-b5+ Black must not interpose
his Bishop, for White will give up his Rook for the Bishop in
order to force the Rook d8 into a pinned position and then he