th the other, and an unexpected check
in some one narrow must be met by the force there present alone, for
it will not be able to obtain immediate reinforcement.

Again, all this line, with its intermixture of sand and clay, which is
due to its geological origin, is a collection of traps for any
commander who has not thoroughly studied his lines of advance or of
retreat--one might almost say for any commander who has not had long
personal experience of the place. There will be across one mere a belt
of sand or gravel, carrying the heaviest burdens through the shallow
water as might a causeway. Its neighbour, with a surface precisely
twin, with the same brown water, fringed by the same leaves and dreary
stretches of stunted wood, will be deep in mud, but a natural platform
may stretch into a lake and fail the column which uses it before the
farther shore is reached. In the strongest platforms of this kind gaps
of deep clay or mud unexpectedly appear. But even with these
deceptions, a column is lucky which has only to deal in its march with
open water and firm banks; for the whole place is sown with what were
formerly the beds of smaller meres, and are now bogs hardened in
places, in others still soft--the two types of soil hardly
distinguishable.

During any orderly advance, an army proceeding through the Masurian
Lakes will strictly confine itself to the great causeways and to the
railway. During any retreat in which it is permitted to observe the
same order it will be similarly confined to the only possible issues;
but let the retreat be confused, and disaster at once threatens.

A congested column attempting to spread out to the right or to the
left will fall into marsh. Guns which it has attempted to save by the
crossing of a ford will sooner or later find mud and be abandoned. Men
will be drowned in the unexpected deeps, transport embedded and lost;
and apart from all this vast wastage, the confusion of units will
speedily put such a brake upon the whole process of retirement that
envelopment by an enemy who knows the district more thoroughly is
hardly to be avoided.

It was this character in the dreary south of East Prussia which was
the cause of Tannenberg, and as we read the strategical plan of that
disaster, we must keep in mind the view so presented of an empty land,
thus treacherous with marsh and reed and scrub and stretches of barren
flat, which may be heath, or may be a horse's height and more of
sligh