soon begin to take
part in the action. But when you are dealing with half a dozen army
corps--240,000 men--it is quite another matter. The turning of any one
of these great bodies through a whole right angle is a lengthy
business. You cannot put a quarter of a million men into one
column--they would take ages to deploy--so you must, as we have seen,
make each unit of them overlap the next before the turn can begin.

[Illustration: Sketch 29.]

[Illustration: Sketch 30.]

Nor is that all the delay involved. It would never do for these six
separate corps to come up in driblets and get defeated in detail; 10,
11, and 12 will have to wait until 13, 14, 15, and even 16, have got
up abreast of them--and that is the third cause of delay.

Here are three causes of delay which, between them and accumulated,
have disastrous effect; and in general we may be certain that where
very large bodies and very extensive stretches of territory are
concerned, that wing of Black which has been left out in the cold can
never come up in time to retrieve the situation created by White's
twelve pinning Black's engaged wing of only nine.

If the square has worked, and if the twelve White have pinned the
right-hand wing of Black, 1 to 9 inclusive, there is nothing for Black
to do but to order his right wing, 1 to 9, to retreat as fast as
possible before superior numbers, and to order his left wing, 10 to
16, to fall back at the same time and keep in line; and you then have
the singular spectacle of twelve men compelling the retreat of and
pursuing sixteen.

_That is exactly what happened in the first three weeks of active
operations in the West. The operative corner A in the annexed diagram
was the Franco-British force upon the Sambre. The retirement of that
operative corner and its holding of the enemy was what is called in
this country "The Retreat from Mons." BB are the "masses of manoeuvre"
behind A. The swinging up of these masses involving the retirement of
the whole was the Battle of the Marne._

[Illustration: Sketch 31.]

Now, it is evident that in all this everything depends upon the
tenacity and military value of the operative corner, which is exposed
and sacrificed that the whole scheme of the Open Square may work.

If that operative corner is destroyed as a force--is overwhelmed or
dispersed or surrounded--while it is fighting its great odds, the
whole square goes to pieces. Its centre is penetrated by the enemy,
and the a