This last political weakness attached to geographical condition
concerns the German Empire alone.

Let us suppose a Power concerned to defend itself against invasion and
situated between two groups of enemies, from the left and from the
right, we will again call that Power A, the enemy upon the right M,
and the enemy upon the left N, the first attacking along the lines XX,
and the second along the lines YY.

Let us suppose that A has _political_ reasons for particularly
desiring to save from invasion four districts, the importance of
which I have indicated on Sketch 12 by shading, and which I have
numbered 1, 2, 3, 4.

[Illustration: Sketch 11.]

Let us suppose that those four districts happen to lie at the four
exposed corners of the area which A has to defend. The Government of A
knows it to be essential to success in the war that his territory
should not be invaded. Or, at least, if it is invaded, it must not,
under peril of collapse, be invaded in the shaded areas.

It is apparent upon the very face of such a diagram, that with the
all-important shaded areas situated in the corners of his
quadrilateral, A is heavily embarrassed. He must disperse his forces
in order to protect all four. If wastage of men compels him to
shorten his line on the right against M, he will be immediately
anxious as to whether he can dare sacrifice 4 to save 2, or whether he
should run the dreadful risk of sacrificing 2 to save 4.