K-f1, Rxb2 discovered check; (8) K-g1, Re4-e2 White must give up
his Queen for the Rook immediately, as otherwise Black would mate
in four moves by R-g2+, K-f1, Rxh2+, K-g1, Rb2-g2+; K-f1, Rxh1+/-.

Although White is still ahead in material after (9) Qxe2, Rxe2 he
cannot avoid the loss of the game on account of the continued
threat which Black exerts by the cooperation of his Rook and his
Bishop. The only move which would save the Rook a1 from getting
lost through R-g2+, followed by a discovered check with
simultaneous attack of the Rook by Black's Rook would be (10) R-
d1 with the idea of protecting the Rook with the King thus (10)
..., R-g2+; (11) K-f1, R-d2; (12) K-e1; but this plan fails as
Black checkmates with (12) ..., R-e2.

A mating position which has not been discussed up to now but
which occurs frequently enough in the actual game to warrant its
special mention is one in which the King is deprived of all
mobility by his own men who surround him and in which a hostile
Knight can check the King. Diagram 42 offers an example.

+---------------------------------------+
8 | | | #Q | | #R | | | #K |
|---------------------------------------|
7 | #P | #P | | | | | #P | #P |
|---------------------------------------|
6 | | | | | | #B | | |
|---------------------------------------|
5 | | | | ^R | | | ^Kt| |
|---------------------------------------|
4 | | | ^Q | | | | | |